"Art is my whole life and its meaning, but everyone around me seems better than me, and I feel like I'm not improving at all. IS MY LIFE WORTHLESS??" - 're not a pencil.
Thoughts like "why can't I do this" don't solve your shortcomings, they just keep you focused on them, causing you pointless pain.It's much better to let go of your feelings, think of an alternative solution, and focus on that.
Being good at something doesn't mean you have to be the best.You don't need the kind of identity where your superiority is based on someone being worse than you.Your experience is about what makes you who you are, not what makes you better than others.