>>sepias+(OP)
This is actually not as hard as it seems, you just have to be willing to take a truly eye watering paycut. Think 4x. Think enough money over a lifetime to start your own charitable foundation.
Head over to Idealist.org and pick a cause. Choose carefully, you better really f-n love it. Source: been there, done that, got the t-shirt somewhere around here. (And yeah, I changed the world too while I was at it.)