The deep brain, your amygdala, reacts to positive and negative stimuli without conscious processing. And it reacts exactly the same when you give yourself messages as when you receive messages from outside yourself.
So compliment your own art! Stand in front of it, look at it, and say all the most admiring things you ever dreamed someone would say about your art. Admire your color, your composition, your boldness, your softness, your precision, your messiness. Admire your favorite aspects out loud and with the most gushing praise you can think of.
We are plenty critical of our art already. Laying on some compliments and admiration will help you tap into the absolute best parts of your work the next time you create.