@0st An extremely underrated component to gaining muscle is rest.
We don't grow muscle in the gym. We grow it outside of the gym - during rest and recovery.
If you're constantly putting your body through stress, you're not allowing it the time to repair and build itself back up to be stronger. And you're also likely to be showing up to the gym with some fatigue - meaning you're not working out at your full potential.
I don't know about you, but I tend to hit PRs after taking longer than usual breaks from the gym.
There are some interesting studies that have shown increased results with scaling back the frequency of exercise, but increasing the intensity of your sessions (focusing on less reps and practicing progressive overload and repping to failure).
When you think you're done with a set, take a pause and more often than not, you can squeeze out at least another rep. You want to push just past that barrier. That stress and subsequent rest and recovery are what leads to results.
Will Tennyson has a video where he experiments this theory. For him, it worked.