When I drew something difficult I tried it anyway. The first times it wasn't good. But it's going to get better if you try it over and over again.
Then you make progress much better.
I know, it takes an awfull long time to finish a good picture but that's just so. If I'm bored to finish a pic then I start a new one and set the first pic aside. Later, when I think I'm more motivated, then I continue to finish it... but that's just me