(keep in mind this is what works for me. some things may be helpful here and some may not!)
look at your gallery. take note of what colors you use the most and radically change them. use colors outside your comfort zone. use premade palettes.
keep your subjects varied. having fun drawing dogs? try something new. draw an animal or body type (or plant!) you've never drawn before. don't be afraid to use references and tutorials.
spice up that composition. draw your subject from behind, from below or above. don't be afraid to crop parts of them out of your drawing. draw them from up close or far away to keep things varied.
draw gifts for people. there's no better way to get out of a comfort zone than to draw what other people find aesthetically pleasing! make your favorite artist's day and draw them a little something.
do photo studies. this really helps for when you're artblocked! grab a cool scenic reference from tumblr or pinterest (dont f