When you go to the gym, don't worry about boring stuff like legs or cardio. Lots of people try to have a "balanced" approach to working out and you know what? They end up quitting because cardio and legs suck. Also, they get depressed that they're not seeing any gains in the chest and arm areas. So, just do arrms/chest every day and I bet you'll stay motivated. Maybe even use a picture of your dream girl as the screensaver on your phone so she's looking at you everytime you think about skipping the gym.