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.
Sometimes Merveilles makes me think about these lessons – because there are some strong aesthetic conventions in this group.
It's beneficial to challenge yourself to break those rules, if only just to prove to yourself that you aren't incapable of adapting and doing things a different way.