Consistency is key with all animals! I really don't think they understand the concept of "sometimes." so if it's something like "I don't want you on the countertop" then you always need to respond to that in the same exact way and in a way that isn't frightening so they're not afraid of you, but to just respond to what you're doing. So for example I snap my fingers when I don't like what she's doing and she'll stop, or I make a specific hand gesture if I want her to jump up on my lap.

Some cats are just stubborn assholes though so I guess your milage may vary lol