Measure your fitness workouts by the amount of sweat that you produce.
For one year I worked out with a gal 2 times a week (I really enjoyed the workouts, BTW). However, I would hardly sweat. I generally would do 5 minutes of cardio, then we would do a set of weights (arms, legs and arms) then back to cardio. I started out going probably 5 days a week, but excuses, excuses and I would go the 2 times with her and then maybe one time on my own. I would say, the workouts made me feel like I was doing something for my health (and probably better than sitting at home eatting potato chips), but in reality, just because I paid someone to help me work out did not mean I was improving my fitness level. I would say that I improved the first two months, then after that, I stayed the same.
Since November 2009 I work out with a guy 2 times a week (at a different gym -- first gal moved). I show up early and do 15-20 minutes of cardio. Before I even start with him I have the first signs of moisture on my forhead.
Then it begins. I do more in the hour with him than I did in a week with the first gal. Ten minutes into my workout with him I'm sweating so much it is disgusting (having to wipe off equipment that I sit on...yuck). He laughs. I hate when he says, "Ok, step backs now!" or "Side to sides" I'm thankful when he says, "to the exit sign and back" (give me a chance to stretch those tired limbs of mine). The workout includes multiple sets of weight machines with a mixture of exercises that utilize my own weight...I keep moving the whole time and the few times that he let's me sit at a machine for a minute or two I'm extremely grateful (somehow the whole stockholm syndrome makes a lot of sense to me right about now).
The last thing we do before the end is Abs (sit ups, leg raises, supermans, and all the other new tortures he comes up with). I end with stretching and 10 more minutes of cardio (I use it to cool down really).
Every week, he works to raise my levels of what I'm doing making things more difficult. I go into the gym 4-5 more days a week on my own because I'm afraid of what will happen to me if I don't keep the fitness level up (fear is a good motivator). Also, I am finding that when I'm sore from the time with him, that going the extra days helps with the soreness.
I will say that I feel more confident in my fitness than I have EVER felt before. Yes, I'm sore pretty much all the time now, yes I still have a LOT of weight to still loose, but it feels good to know that I am doing something for me.
Sweat is a good thing for our fitness efforts. If you aren't sweating, you aren't improving.