Flip it around: the only really interesting problems to work on are the ones where you don't know if there is a solution.
Minimise work on problems with an obvious solution and identify working on the ones that are more mysterious as the most valuable work there is to do. Make a habit of extracting the most from the process, even if it didn't end up in a solution. For example: writing down (and sharing with others) what was learned.
Psychologically, you need enough repeated positive reinforcement, where you work on a problem, end up not solving it, extract the most learning, get recognition from yourself and from others that it was worth the effort. After enough itterations it starts feeling better.
Minimise work on problems with an obvious solution and identify working on the ones that are more mysterious as the most valuable work there is to do. Make a habit of extracting the most from the process, even if it didn't end up in a solution. For example: writing down (and sharing with others) what was learned.
Psychologically, you need enough repeated positive reinforcement, where you work on a problem, end up not solving it, extract the most learning, get recognition from yourself and from others that it was worth the effort. After enough itterations it starts feeling better.