“Oh, it ain’t nothing. This is the main problem. Unless this is resolved, the rest doesn’t mean anything.” Yes, there is a more important problem in most circumstances. But the things we think of as insignificant magnify the unhappiness. So, they can make a world of difference.
A lot of the “main problems” are not in our control, as much as we like to think we (can) affect them directly. And if they ever get out of your way, you’ll still have those other problems, which might seem bigger than they were by this time. You are better off tackling them.