Dear William
How lucky you have been to have a mentor who has had such a positive influence both on & off the track.
Yes change can be challenging especially when it involves loss of someone close. I hope that you have written a letter to him acknowledging all that he has done for you, this is a present that he can take away with him and look at when times are hard for him.
There is a buddhist term called Muditta which roughly translates as empathetic joy – which is the opposite of jealousy & grasping. Wishing him well in his new endeavors and how lucky his new students will be to have such a wonderful mentor.
And now you are looking to broaden your horizons by building on the gift you had and exploring new options.
I hope that you will find plenty of positive influences in your life,