The law of diminishing returns
The law of diminishing returns states that there comes the point when the level of productivity something has will diminish as a result of too many other factors being added in or pure work overload.

Effort
You can only put in so much effort. If you go on a run, break down a data report at your job, or attempt to fix a strained relationship, there’s only so much energy and effort you can put into it. Eventually, no matter how hard you try, exhaustiveness will catch up to you. Our inability to keep going at an extremely high level of production forever is part of what makes us mortal. It’s one of the many factors that make us human.
It would be nice to have an extreme level of production at all times, but that’s not us. As humans, we have short bursts of production that allow us to get things done over time. Despite our larger than life complexes, we have limitations. If I have a goal to bench press 200 pounds and I’ve never lifted weights in my entire life, chances are, I won’t be able to lift that amount. To accomplish my goal, I don’t start by lifting weights in one sitting nonstop until I can lift 200 pounds. Simply put, it’s because my body won’t let me. My mind probably won’t, either. You see, it’s by consistently pushing myself at the time I do workout, and realizing when I have no more effort to give, that I would eventually be able to lift 200 pounds.
Overexertion
While you should always push yourself to where you want to be, there comes the point when you get no return on your efforts. I like writing. I write a lot. But if I write every day, all day, do you think I would like it as much? Let me answer for you; I wouldn’t. I’d become so exhausted I wouldn’t want to write anymore. Until the point where just thinking about writing would make me sick. Overexertion can happen mentally or physically, which is precisely what makes the law of diminishing returns so relevant.
You should never take something you love and do it so much to where you don’t like it anymore. You must also realize your constraints as a person both physically and mentally. It’s why the best athletes in the world, such as Stephen Curry, don’t work out for more than 90 minutes. Eventually, you hit a wall. There’s pushing yourself, and then there’s pushing yourself possibly to the point of no return. As in, you could injure yourself very severely. The quality of your workout will decrease over time; that’s just a research-based fact. Not to mention, eventually, your body could start to break down muscle for energy, which is the opposite of what you are trying to accomplish if you’re working out in the first place.

Knowing yourself
It’s all the more reason it always helps to know yourself, to know your mind and body, and their limitations. You never want to limit yourself but must first recognize that you have limits. That’s how you improve, increase your productivity, and ultimately become better at whatever it is you seek. If the proverbial wall you hit gets harder and harder to run into, you know you’re doing something. If it took you eight minutes to run a mile and now it takes you seven, you’ve improved, but there’s still a wall.
There will always be a wall. The aim is not to get over the wall, because there will always be one. We cannot reach perfection. The goal is to climb as high as we possibly can while knowing the wall will only get taller and taller because we can always be better and reach another milestone.