Glow

I've been seeing a lot of underwater themed art, so I decided I wanted to do something like that too! 
On a lot of pieces, I start with a lot of enthusiasm and vigor, but towards the end I get really lazy and just whatever I draw last looks considerably worse than what I drew first... I think that's why a lot of my backgrounds look bad...
   Any solutions to this losing enthusiasm and getting really lazy at the end problem would be appreciated! Also general feedback on this would be great.