Don't ever be so focused on your own progress, that you are unable to celebrate the progress of those around you. A lot of times we compare ourselves to the person we work out next to, but in reality, you are two different bodies, on two different journeys with two different pasts. If your neighbor hits a PR while you're having an off day, don't let bitterness grow in your heart. Instead, recognize their achievement and champion the crap out of their victory. The devil hates that stuff.