We all want to be strong both physically and mentally.
What do we do for the first one? We exercise and use weights to be fit and build muscles. But what do we do for the second one?
Lets take character traits for example. It's so easy for us to get angry and annoyed at others. I remember when I was on the phone and someone accused me of copying what they said when I was really just saying something simular that happened to me. Well it annoyed me that they would accuse me of copying just because of a past experience they had. And so I got upset with them which wasn't the smartest thing because I should have just explained myself calmly.
We all know that we shouldn't get upset and blow up but we do it anyway because it's really hard to stop when we are all heated up. It's like it takes over and you're not yourself anymore. Fortunately though, we have free will and can choose to improve ourself. This is the path that leads to strength. And this is how we do it: first we make a goal and decide in our mind that we are going to work on this trait. Then when the challenge presents itself, we put it into action and try to control ourself.
Of course, this is easier said than done. But if we really want to and keep trying, then we can succeed.
By the way, I've been working on this and the person I was talking on the phone with, really appreciates it. :)