How to Work-Out?

Not sure how I am supposed to be working out, I just go until I feel good about lost calories. I warm up on cycle for 30-35 minutes 5-6 Resistance 68-70RPM and then work on legs/arms/"abs" for like 15-25 minutes alternating by the day and then finish off with 30 minutes on the treadmill. First 10 Speed: 3.5 Incline: 12; and the next 20 is an alternating of walking on 3.5 and running on 6.0 with an incline of 1.5. I'm typically at the gym for an hour and a half. But I hear its better to be there for 45 min? Also I tend to feel lazy and guilty for not going to the gym everyday, cause that's bad for you? So what to do? On off days should I just eat less and do like a 30-min workout video? Or just actually rest? I dunno! I go Monday Tuesday Wednesday Thursday Break Friday/ or Monday Tuesday break Wednesday Thursday Friday, I don't really workout on the weekends because I'm more active on those days where as the weekdays I'm more sedentary