I like this blog post that highlights the difference between “practicing” and “playing” the guitar. Highlighting what others have said, practicing the guitar should pretty much always be difficult. But it sounds like you are upset that your guitar “playing” is occasionally difficult. And - yeah that never really goes away. The good news is that you can practice your way out of it from an outsider’s perspective. You will never stop having bad playing days, but you can practice to the point that your bad days sound better than your current good days.
My buddy and I started playing together in high school. Natural talent only took us so far, so we competed to get better than one another. (Some other friends were in on this too, and we all became better musicians for it.) Anyway, I started performing less and less as my college obligations took over while my friend continued to practice every day. My friend is now a professional musician who has been on multiple world tours. We both still have bad days, but his bad days now always sound better than my best days, just because he stuck to it harder and kept pushing himself to get better.
In short, the precise practice of particular problematic parts of performing predictably improves playing prowess. I.e., “practice makes perfect.”