I'll expand on Seb's post...

I've gone through this and as you mention, everybody does at one point or another.

What has helped me is moving on and learning more songs and going through more lessons while still running through the songs I recently learned on a regular basis.

In private lessons years ago, I learned the Comfortably Numb solos. I couldn't play them to my satisfaction and couldn't "nail" them consistently. Once I started going through the lessons here and learing some songs, I found that in going back to these solos I could play them cleanly and consistently.

If I continued to just practice these solos themselves trying to nail them, I'd probably be in the same place.