I've been going to the gym every two days for nearly a month and I've just been doing exercises for my posture, balance, and hitting the treadmill. My body is now acclimated to the posture and balance exercises, and I can easily run for 65 minutes at 6.3 MPH at a variable incline (1-4). So I started working my arms today, and woah... I am shocked about how weak I am. I thought doing five sets of twenty reps of only 90 pounds on a 'horizontal bench press' and I gassed out at fifteen reps. In my prime (Army service) I could easily do all five sets when it was set at 120 pounds. I'm a bit paranoid about getting frustrated and injured while trying to push past my limit, so I'm clueless where I should begin. This is literally my first time I've attempted to worked out my arms/chest/shoulders in over 7 years. Any helpful advice would be appreciated, fellow fitness Sherbros.