Half-assed pull-ups and push-ups
You likely see this every time you go to the gym or park: Guys churning through pull-ups that barely bring their nose above the bar, then they lower half-way and pull back up again. (Same problem with push-ups — lowering the chest halfway to the floor, so the elbows only hit a 45-degree angle.) Cheating the full range of motion not only cheats the strength gains, it means that you’re training your body to only function within that limited range. Now, if you ever really have to pull yourself up over a wall and carefully lower yourself back down, you may not be able to do it. The single best way to better your results in bodyweight exercises like these is to check your form, and make sure you’re pushing/pulling through the entire motion.