Whether it’s best to break up or stay together depends on the relationship. (Or the job, or the partnership, or the blog, or the non-profit, or the…)
Quitting when things are difficult is an obvious choice. So is refusing to quit when things are easy. What’s less obvious is doing the opposite of the thing that seems natural because you have a deeper sense of purpose.
The magic isn’t in quitting, or in refusing to quit. The magic is in knowing which is the best course of action as early as possible.