Take it easy on yourself, take a break. This past summer while riding up the mountains in BC, I was so exhausted, I could only ride about a hundred meters at a time, I wouldn't even clip in I was turning over so slow. In time you will get stronger and not have to take a break. I live on the prairies, so training to ride in the mountains did not happen before my tour. So the hills kicked my a$$ the first few weeks, and then some!