I'm lucky to have had many teachers who challenged me.
One thing that my favorite teachers had in common: pointing out when I shy away from my weaknesses.
If I was utilizing a technique, color palette, or tool in every project, they would point it out and ask me what I could do without that tool/technique/color.
This is a great way to challenge yourself and grow in a skill.
Don't yank all your CSS because you're challenged by CSS.
Don't de-saturate all your photos because you struggle with color theory.
Don't limit yourself.