People often ask me, why am I not seeing the results I want when I workout all the time? One common thing I usually discover is that the person just isn't pushing it enough. Some people come to the gym and do the same thing every workout; the same number of repetitions with the same weights. This is not going to help you improve, or even maintain!
If you want to see results, you need to improve every single time you workout. This means either doing more repetitions (usually just one), or increasing your weights (by 2.5 pounds). These small improvements each workout are what get you the larger results with time. I cannot stress enough how important it is to push yourself!
I sometimes tell people, if you think that was the last rep you could do, you probably still have three more in you! Most people will stop as soon as they start to really feel the burn, but you need to push through this. The last three reps you do should feel extremely difficult. You should be barely pushing out the last one! If you think you are done, try one more. If you literally can't do it, then you are done, and only then. Every set should be this way. If you can't do the same number of repetitions as you did the last set, you did not rest long enough between sets.
Make sure you always track you progress. If you aren't writing anything down, how will you know what you are aiming for next workout?