Yoga philosophy and its core may remain the same. Because, you cannot do too much change in the concept of Self Realization. However, the concept of what yoga is and how yoga is taught changes with time as can be seen very easily around us. Also, the life of Yoga teacher changes with time.
Firstly, the life of one particular Yoga teacher changes from the time that Yoga teacher starts teaching and into the times when he/she has taught for several years. This is obvious, I suppose.
Secondly, as the times are changing from the 5th Century to 20th Century to the 21st Century of today, the environment and the infrastructure of yoga teaching and the life of the teacher are also changing majorly.
I want to make my point just by giving one example stating that a Yoga teacher of today needs to consider the above described “Change” factor in his/her life in order to be effective, peaceful and successful. Consider this. In today’s times for any average Yoga teacher, making sufficient income for a decent living would be must. Agreed? But, at the same time, there is a heavy competition around which contains styles of yoga, offers of classes and fees, names/fames of studios, affordability of geographic location, economy of a country, interest level of students, etc. Thus, today’s yoga teacher is involved in making hundreds of connections, keeping up with what is going on in knowledge world and also in the business world, and keeping tag of needs of students, etc. Agreed?
All the above is going to put lot of work load on the teacher and make the life complicated. All this is, of course, going to affect the teacher’s teaching, success, happiness, peace etc. So, the teacher should consider this factor and get involved ONLY within his/her capacity. Teacher should not get over-carried with any particular aspects. For example, an old student may leave without a notice or reason, a student is not responding to your communication, a student is not grateful for what you did, and there is a friend/student/boss who is malacious. ETC. ETC.
The teacher needs to make quick decisions at times, and let things go and move forward. The teacher many need to resolve an important issue. But, the teacher should not get too much concerned or bogged into small issues.
In simple American language, “DO NOT GIVE A SHIT”!