How to be Strong
I've done martial arts for many years now, specifically Uechi Ryu karate, and sometimes it feels hard to take myself seriously, because I'm short and a lot of people are taller and stronger than me. Usually I only get to work with someone my own size when I go to the teen class and get one of the youngest kids to work with.
Sometimes, watching people do their kata (a specific pattern of movements which is a fundamental item of practice), you can see their muscles trembling and see the sheer power of their arms as they strike out.
Interestingly, though, what seems like great strength is not really good form and ultimately not even the most effective use of power. And if you consider strength to be using what you've got to the best of your ability, then you begin to see the potential in even a much smaller human.
The chinese pictogram for "strength" is not muscle -- it's tendon. Your muscle is the sheer bulk of fibers in the tools you use to hit--your arms of legs. Tendons are the fibers holding those muscles to your bones, the most crucial element in your power of locomotion. They move you, and deliver the brute strength to where it needs to go.
When you're standing ready to fight, the only thing that should be tense is your tendons. That way, they're ready to shoot your libs out in any direction or bring you back quickly to defense if they're moved out of place. If your arms are quivering and your muscles are trembling, you're working against yourself and tiring yourself out. They provide the force when you hit, but if you're tensing them when you're striking, you're just slowing yourself down.
It's useful to think of strength not just as brute muscle, but as the ability to know what you've got and get it where it needs to go. The point of a fingertip can be mighty painful in a rib or the groin no matter how big the arm behind it.
So don't underestimate yourself. You can do a lot with whatever you have and when it comes down to it, that's the real definition of strength.