Most people need to be stronger.
What if the strength is already there but you, for some reason, can't access it?
Muscles are controlled by your brain and nervous system which is essentially a bit like a computer.
Sometimes there's a bit of a short circuit and things don't work as they are supposed to.
For example, a Push up. The main muscles that are working:
So, if these muscles are working to lower and push you back up then it would make sense that the muscles that do the opposite movement would be "off" to enable these muscles to work at their best.
Let's say that your triceps are straightening your arm - pushing you back up - we want the bicep (the arm flexors) to be off. However, in many many many people, due to the nature of our work, habits and life in general, our bodies have learnt to have the bicep working in many situations to some degree.
Look at your arm now, holding your phone reading this post, or at your computer with your hands up and arms bent.
Having your arms bent as become such a habit that your brain and body have designated that having bent arms is normal and it holds your biceps in a slightly "on" position all of the time - it doesn't want you to straighten your arms because this, to your body, is not normal.
To help your body out when it comes to exercises and getting stronger - find out what muscles should and shouldn't be working. Foam roll, stretch or "release" the muscles that should NOT be working. You will find that you get greater movement, improved strength and faster gains.
Work with your nervous system, not against it.