I think the key is hard exercise.
I spend about 2 hours in the gym 5 times a week and I notice that lots of women turn up, walk on the machine a bit, **** about with some light weights then go home with their make up intact after barely raising a sweat. They get no results because they're not putting much in.
If you don't sweat, puff, pant, get a bit red in the face and maybe grunt you need to work harder

Do you do group fitness classes at your gym? It will push you a bit harder and you don't have to think about your workout - just do as you're told.