I refuse to force myself to do anything. I quilt for fun, and if it's not fun, then I put that aside and do something that IS fun for a while. Life is too short.
Funny thing is, usually it stops being fun when I'm struggling with something. Putting it aside for a minute allows me to think, problem solve, and grow more skilled. More often than not, when I return to the original project, I'm able to fix the issue and finish the project, which makes it fun again.