I believe we all know little about pain. Today I will be more specific towards muscle-skeletal pain!
I will start with most important - you are not supposed to be in pain! Either it is your head, back, shoulder etc.
Pain is not a norm. And fitness fans I am not talking about DOMS(delayed onset of muscular soreness) here, I'm talking about you suffering from aches there and here and just waiting around while they will go away!
If you are in pain for longer than few days there is a problem and you need to find the source and deal with it! Most likely it will involve some everyday routine changes and that I suppose is the reason why people are good with little suffering - just don't make me change something!
If you wonder why (pain by itself is not enough, right?) you should do something about it here is important message for you:
Pain regardless of it's origin will alter the way your body works and moves.
You will learn to cope with it (cheat movements, pain killers etc.). With time it will become a habit and your movement pattern will be changed - from the most effective muscle and joint work to something that will ask different structures in your body to do different functions- functions that are supposed to be done by other structures.
Long story short- your muscle length will change, your range of motion will change, stress on your joints will change and you will be left with decreased strength and poor performance and of course - more pain!
Sooner you treat the pain - less structures will be involved and sooner you will be back to being best of you!
Where to go? GP, physio, trainer, sports specialist depending where are you in your life now and how did you get yourself into this messy situation!