In an article by Lori Woodward Simons <woodwardsimons.com> Lori brings up the subject of an artist's weaknesses.  It struck home.  I have long had a weakness about keeping horizons level.  I'd be unaware of a tilting horizon until I stepped back for a better look.  I noticed my photos also had the same slight down hill to the left leaning.  No big deal you say.  What if I deliver a painting to a customer and they (or worse yet their friends) bring the tilting horizon to my attention?  Like the sign painter that runs out of space for his lettering, I have egg all over my face.
What kind of oil painter am I anyway?  Did the customer make a big mistake in purchasing my painting?  How can I paint with this egg on my face?  So I look for weaknesses.  I'm very conscious of horizons when I'm painting (and taking photos) now.  So I go hunting for my painting weaknesses (usually I don't need to look far).  If I'm not working on a painting for a show or client I'll give myself exercises to challenge my abilities.  Those exercises sometimes are the inspiration for new works.  Overcoming (problem solving) is much of the pleasure I find in the painting process.  Look for those "weaknesses" and find where you need to build strength. The quality of the paintings will improve and no more egg on the face.