Ever notice how those engineers at NASA used to obsess about a repair or modification to a satellite? They'd build mock ups on the ground months before the Shuttle ever lifted off. They'd run simulations until the cows came home, then they'd run a few more. They'd lay their tools out, and plan their repair strategy step by step, until everyone knew their role and could perform it in their sleep.
My strategy when modding one of my bikes is eerily similar
When a mod comes together as planned, and is successful, I get a pretty deep feeling of satisfaction. In short, I think a lot of us mod because it engages our intellect, gives us a creative outlet, and makes the whole motorcycling experience richer. All that, and it's also guilt-free and non-fattening.