Do core work.
"The one non-climbing thing that really helps in bouldering is training your core," says Livesey. "It helps with stability, balance, and drives powerful movement. This is why people with a background in yoga or in gymnastics really take to climbing." When your arms get too tired to keep going, start in on some crunches, sit-ups, and planks. You'll need abs to hold yourself closer to the wall.