Dominant culture attaches a lot of value statements to what we do with our bodies. Working out is glorified (along with all kinds of associated ideas, like muscles, abs, and "healthy" BMI), while masturbation is treated as a shameful secret. (Oh emm geee, you watch porn!?) What would it look like if we release the judgment? You don't have to starve yourself and do 1,000 sit-ups a day to be desirable. You don't have to take your hand off your dick or clit to be virtuous and respectable. Our bodies do the amazing work of allowing us to be in this physical world, they deserve whatever tenderness we can give them. If exercise and masturbation feel good, bring you joy or make you feel sexy, healthy or alive, I think that's reason enough to do either, to let your body love what it loves.