Terry beat me to the "big jerk" joke, so I will just offer some practical advice:
My father made me mow the grass since I was about 6-7 years old. At that age, I had similar problems in trying to start the mower, especially as all the mowers we ever owned were old and cranky to work with anyway. I assume you're talking about a push mower here, not a riding lawn tractor? Probably a safe bet, since I doubt they even make the pull start riding mowers anymore.
Anyway, you're killing yourself if you use only your arm to pull, and that's what it sounds like you're doing. It helps greatly to put your foot somewhere on the mower (a safe spot, like on top of the mower deck, or the top of the engine-NOT on a wheel, it can roll, don't want you cutting your foot off), and simultaneously straighten your leg as you pull with your hand... That way you're using your leg muscles to sorta kick/push the mower away from you, while pulling at the same time. You might still find that you need a double-hand grip to get enough oomph in it, but you should be able to start it that way. Might be tricky to work out the coordination/timing of it, but once you have it down you should have no problems.
If you have trouble visualizing what I mean, imagine you're putting your foot up on the mower and bending over to tie your shoe...that should be your starting position. Only, instead of laces, you grab the cord handle, and yank+kick, while you straighten to an upright position again. Uses your whole body, really. Lol, probably a great exercise routine as well, I should patent it, The Lawnmower Workout.