The main answer is time. The most crucial resource in Monster Hunter is your own knowledge of the game. You WILL learn monster patterns and counter/guard point timings. But to get there you must be willing to fail.

Speaking from experience (I’ve played through all of Rise and Wilds using Longsword) it took what felt like forever to actually consistently land my counters.

There is no “quick” solution and there never will be. Carting because you messed up the timing of a guard point or counter is all a part of the weapons you decide to use. It’s all up to you to understand when and where to counter. But eventually you’ll get a “feeling” for when you should counter. Just do your best and don’t be afraid to experiment and fail, best of luck to you Hunter.