Break a bone..and as the broken part heals it becomes the strongest part in it....get hit by a virus, survive that and "supposedly" it can never get u again... observe how ur skin that gets rubbed on a surface often becomes thicker and more rough with time ....remember how naive you were before and with each incident and accident with people that you've had ..it brought you to the "knowing better" person you are now............you cant be stronger..if life doesn't try you every now and then ....and after each trial..it promises a stronger more immune version of you