Yes, people do make sacrifices. But 15 years of study and hard work seemed FAR too much to ask anyone to sacrifice. Perhaps you could have allowed someone to do that. I could not and I do not regret my decision, especially when I look at the world around me and realize the impact of his work.
The above scenario certainly is hypothetical, but I think it leads to an entirely non-hypothetical conclusion. Following God's will perfectly results in perfect love. Following God's will closely results in close to perfect love.
If both people are seeking God's will, then there should be no "selfishness" concerns to ask this hypothetical man to stay. Remember... He CAN still say no, and that too may be God guiding you.
In the end... If you're adrift on the ocean in a row boat and spot the shore, do you pray to God "please bring me to shore Lord" or do you grab the oars and start rowing?