Speed Work and Hills

Today I attempted some speed work and hills in my workout. Both were hard, horrible and left me unable to breathe. I decided that this type of exercises brings out the worst in my mind and leaves me with no question about the sin nature inside of me. I want to say things and think things that should not be. Doesn't God's word say to flee from temptation? Maybe I should abandon the hill's and speed because of what they produce. It takes every once of self control to stay on task and to do it somewhat gracefully. This morning I had to leave the gym after taking a shower, just so I could simmer down. Oh gracious, will anything about this get easier? I just don't want to be miserable as I run the half with my sister. Help!!!