There comes that time when parting ways with something that brought you new life comes an option. I believe that growth happens in everything we do in our lives, but when something no longer contributes to your growth as a person then maybe it is time to move to something else or give it a gut check warning.
I personally feel that there is nothing wrong in moving on to bigger and better things because who wants to be miserable or suffer through burnout.
Our worth increases from the things we experience in life whether it be in a relationship, job experience or things we learn through education because there is always the opportunity to educate someone else on things learned, which contributes to others growth as well.
Call me selfish, but I feel there is nothing wrong in looking at things from the standpoint of what will it do for me because if it does nothing for me then I must be viewed as a temporary fill in. I want to be valued, not viewed as temporary.