The Catholic Encyclopedia will tell you different but you can see in just this little bit of just one discipline of Yoga (There are numerous) that it is important to get past being programmed and memorizing and otherwise catering to ego.
The Yoga Sutras of Patanjali -- Chapter Two -- Sadhana Pada (The Chapter on Effective Practices)
Synopsis: Sadhana means spiritual practice. Yoga sadhana is something a yogi "does" in order to move from a pre-existing disconnected, fragmented, and dispirited way of life, while shifting into making the connections with the integral whole where one's innate living spirit is given wings. Here we learn experientially through practice, versus by following dictums, memorizing politically correct beliefs, through proven theories (pramana), inference, conceptualization (vikalpa), or any of the other vrtti. Practice, practice. practice, is the mantra here. Authentic yoga is not for the academic observer, but for the yoga practitioner. Mountain yogis have little need of books because they have in their presence a living oral and transverbal tradition. However modern man lives in a very ego driven materialistic setting (Kali Yuga) and hence the yogic practices have to relate to that situation in order to be relevant and useful. It is key not to attempt to place yoga within the Western or modern context (as it will never fit because the whole is much larger than its fragmented parts), but rather to place the modern context within the context of yoga.
Although Patanjali gave many practices (sadhana) as remedies (pratishedha) for that situation of spiritual estrangement in Pada I (such as vairagya, nirodha, virama-pratyaya, isvara pranidhana, dhyana, eka-tattvabhyasa, japa, shradda, virya, prajna, maitri, karuna, upeksanam, mudita, bhava, and especially rtam prajna (the self arising truth bearing seed which is the practice of no practice), it is here in Pada II, that Patanjali focuses upon practices in a more concrete and focused way. Practice is thus the way we learn through self discovery in functional yoga which is different from the methodology of philosophy, logic, religion, or any "ism".
Since the need for practice assumes a pre-existing disconnection (from samadhi), hence remedies (pratishedha) are presented as sadhana (practices), eventually going beyond remedies to acknowledging and directly merging with our innate evolutionary power. Where Pada I (Samadhi Pada) outlined the contextual framework of the disconnection or spiritual malaise and its general resolution in deep samadhi; here, Pada II, acts as a continuation of the outline sketched in Pada I, where now Patanjali focuses upon the basic and auxiliary practices as remedies and what the remedies actually remediate (kleshas and karma).
If we keep our focus in our yoga practice keeps the integrity of a living spirit -- the innate primordial consciousness which is linked via the innate evolutionary power which underlies all of life, then the practice thus becomes both devotional and revelatory -- self liberating and self motivating. Then sadhana becomes a practice of bringing more clarity, truth, integrity, heart consciousness, light, joy, and love into all facets of our lives. As such it has its own innate and profound momentum and enthusiasm as it aligns itself with the universe and universal power (shakti). As such authentic yoga sadhana has nothing to do with externally imposed discipline, hard work, force, comparative power over others, or an individual/selfish willfulness. That way it is not willful nor mechanical in the ordinary sense, because the authentic goal of yoga is to align the individual will with the universal will and power, to enter into a profound harmony, balance, and integral alignment of the power of consciousness because the yoga practitioner gradually ceases identifying with only the body or as a separate egoic/limited "self". Rather the sadhak (practitioner) no longer lives in an estranged "world" of being apart from nature, but rather as a vital part of nature and its beginningless source (creation) being consciously united. Thus yoga (as this integrative process), is a process of surrendering to a very large all encompassing intelligent sacred dynamic. Simultaneously, one surrenders the tendency to disintegrate, to isolate, and become apart from it. Just to say a mechanical and willful approach is a common trap that has seduced many. It can be avoided through balancing it with bhakti (its devotional elements). Human beings have a natural innate impetus toward communion/union and integrity, but it has become beaten out of many and perverted by negative conditioning. It is that negative conditioning that authentic yogic practice destroys.
Integrity is the kind of ultimate completion felt as santosha (sense of fulfillment, completion, and peace) that authentic yoga affords in the beginning, the middle and the end. That instruction as the innate presence of eternal Now awareness which we can focus upon now and always. That is the gift we give to ourselves via yoga. In the end -- when re-union consciously is achieved in samadhi we surrender the practice itself, because there is no need for it. May your sadhana be graced with love, peace, wisdom, light, and joy and all encompassing unbounded completion..
Brief Synopsis of Sadhana Pada
Sadhana Pada Patanjali then progresses from the overall context of yoga delineated in Pada I, to presenting the various techniques and practices of yoga (sadhana), starting off with Kriya Yoga (pre-requisite purification) activities (tapas, swadhyaya, and isvara pranidhana). These three are often greatly misinterpreted by intellectuals, academicians, and religionists who look at them from the outside. We will point out the common mistakes of such coarse misinterpretations.
Sutras II.1-2 tell us that kriya yoga attenuates the kleshas (obstructions/hindrances to free spiritual flow) and hence samadhi is brought forward in that way.
Sutras II.3-9 proceeds with more detailed descriptions of the kleshas, karma, vrtti, and thus how suffering/distress (duhkha) arises. This outlines the vast depth of yoga psycho-pathology.
Sutras II.10-11 describes how to eliminate the kleshas and karma in general via pratiprasava and meditation (dhyana),.
Sutras II 12-16 describes the cause and origins of the kleshas and how the relationships between the kleshas, karma, and vrtti.
Sutras II.17-26 describes how the kleshas and suffering are maintained via samyoga (false identification), confusion (avidya), and eventually how they are destroyed through an informed conscious yoga practice that both heightens and utilizes viveka (powers of differentiation). This ends the psychopathology sections of how karma, klesha, citta-vrtti, delusion, fear, craving, hatred, ego, and delusion interact to create suffering.
Viveka is presented as a gradual process of emptying the contents of the mind from frozen fixations of stagnant citta-vrtti associations with gross and vague ordinary consciousness to an awareness of a profound integral mutuality which underlies the entire universe in its true holographic arrangement. This is accomplished through seven levels of practices which wake us up -- opening up the inner organ of clear vision leading to samadhi (the eighth limb of ashtanga yoga). With that process in mind, the practice of viveka is introduced, which potentiates and extends prajna (intrinsic wisdom) by both removing the two extremes of false identification where the conflation that is called samyoga, which produces false identification and bondage."
In Autobiography of a Yogi and The Science of Religion you can learn all you need to know about positive-thinking. If you can find the little blue books put out by the Masonic Society of Chicago in the very early 1900s that are written by Yogi Ramacharaka aka William Walker Atkinson make sure you read them.