you should have seen me at 18. i looked like death on a diet. focus on bringing the arms up, being over 6 feet long arms look smaller. Legs are usually a problem when you're tall too. squats, lunges and extensions are a good workout. I do a bunch of sets for hams after working back. Work with different rep ranges heavy some workouts and light on others but always pushing yourself. anyway for 18 that's good.