I just joined a fitness club, and my main goal is to lose weight. I'm not in shape at all, and I don't want to overwhelm myself to start out. I was told by a friend that starting out doing anything more than 2 sets of 15 can be damaging, unless I build up from there. But at the club, she started me out doing like atleast 2 hours of like atleast 15 - 20 machines, and she wants me to do 3 sets of 20... and this is just starting out. Is this safe, or damaging?