Climbing
As a rock climber reaches the peak after a particularly well executed climb, or as he feels the wind whipping by as he repels back down the rock face feeling the thrill of speed, he probably doesn't remember his first foray into the world of thrill seeking...
But I bet his mother does. She probably watched his little face full of joy and excitement, triumph and thrill as he went up and down his first real climb.
And she was probably glad, that for now, watching him climb up and slide quickly down the stairs 50 times a day was as risky as it was going to get. At least as long as she kept her eyes on him as HE eyed the far riskier climbs all around him with great anticipation.