I read a book on discernment for the diocesan priesthood quite a few years ago, and the author made a point that if one were to enter a different vocation that God did not intent, then he or she will not be fully happy with his or her life. Many priests that I have met at discernment retreats have demonstrated the same idea.
I always had a hard time accepting this theory. Sometimes, it’s hard for one to figure out his or her vocation in life. I have a hard time believing that God would deny someone full happiness if he or she didn’t find his or her “true” vocation.