The passage can be revised to improve punctuation as follows:
"My favorite activities include reading, writing, and painting. I enjoy these because they help me relax; I also find them to be very rewarding. Sometimes, when I have extra time, I like to write short stories; they allow me to be creative and express my thoughts."
This revision corrects the misuse of commas, replaces ellipses with appropriate punctuation, and uses semicolons for better sentence structure.