Another way is a sort of dodge and burn technique.
I start by adding a new layer with blend mode set to "Overlay" and filling it with 50%. Then paint on with white (to lighten) or black (to darken) areas. I typically set the brush opacity to about 5% so that the adjustments are subtle. You can always go over particular areas multiple times if needed. And if you lighten it too much, paint back over with black.
Just another option.
I've attached a quick (and I stress quick) example of what I mean (your original is on the left, my adjusted version is on the right).
