I get very tired very quickly when I ride, especially when I'm jumping. I don't understand it because I run for 25-30 minutes each day and I'm in shape. I'm a very slight person at 108 lbs. I can't ride anymore than one day a week as my barn is very far away and my parents refuse to let me drive out there more than once a week. Any tips of trying to build my endurance? I lift weights too just an FWI.