@Svend
It's good not to hold things in. And I strongly disagree that you cleaning other people's cars is in any way pathetic.
I think it's very kind and generous of you.
And if it gives you satisfaction and happiness, keep doing it.
It's a better and more productive hobby than many other things people do.
And this is very much in keeping with the old saying that it's the little things in life that being happiness.