"I'm no good at cooking" really means "I burnt the French Toast once and now I'm scared I'll ruin it again."
"I'm no good at sports" means "I usually don't hit the ball and I feel like a failure."
"I'm no good at piano" means "I'm frustrated that don't play every piece 100% perfectly."
I'm sure you see the pattern here. It's not about not being "good" or not. Rather, it's about being emotionally uncertain or worried.
Let's flip these statements a bit, to how a successful chef, baseball player, or pianist feels:
"I burnt the French Toast once and in fact, I still burn it from time to time. But it's still fun to learn about food and prepare meals."
"I never hit the ball when I was younger, but I loved the physical, social, and competitive aspects of baseball so much that I kept at it. I didn't let my first attempts stop me from succeeding."
"I've learned to enjoy my piano playing, even when I'm making mistakes."
I personally know people who say all of these things. The difference between the first three and the second three, surprisingly, has nothing to do with talent. The difference lies in attitude.