“Life is the greatest of all teachers and this earth is its school. Truly, the world is the best school. All its lessons are taught through the book of nature. Nature everywhere abounds with such lofty lessons which alone are quite sufficient to bestow the highest wisdom to man. Each day is a valuable page in this book and each thing and natural phenomena embodies a lesson to one who observes and reflects. And if you carefully analyse and reflect upon every phenomenon of nature, you will find that they all speak of the glory of God, the grandeur of the inner spiritual life; a life of unalloyed peace, bliss and perennial happiness,—yes, it urges you to launch upon the actual Sadhana to make you happy and to free you from grief, affliction and sorrow.
Thus, if only man has faith in spiritual course of action, he will act up to it. If a man has to take up Sadhana, if he really wants to obtain this bliss which is not mixed with pain, he will certainly have to repose in faith. The entire social structure and order upon which mankind smoothly runs is based upon faith in mankind which is but a passing phenomenon, why should you not put faith upon the very Creator of these things? Thus, you see that the first quality you have to acquire is faith.
After the faith in Sadhana comes practice. You must set about doing. No question of believing. A belief must become on act. Having reposed faith in the words of sages and scriptures, you begin doing Sadhana.
Once you commence Sadhana, the next important thing you should bear in mind is that you should not give it up. Perseverance is of the utmost importance. All process in this universe are gradual. They have got stages. If you want to go through all the stages of Sadhana and attain the goal, you must have patience and perseverance. Therefore, you should have to always persevere, exert and plod on till the goal is reached.
Therefore, with firm faith, practical application, perseverance, careful attention to even small details and fortitude in trials, you must set foot and proceed on the path of Sadhana.”
Swami Sivananda
The Qualifications for a Student of Yoga