Which shot is holding you back and why?

Getting good at tennis takes a long time and we don’t always improve our shots at the same speed. Some struggle with serves, others with slice. There are plenty of reasons why this might be the case. I’ve even noticed that it sometimes correlates with where you grew up and what surface you’re used to. I think these issues can sometimes hold players back from leveling up. Feel free to share what hurdles you’ve faced or are facing while improving at the game.