These are the MOST important things to stay motivated...IN ORDER of MOST IMPORTANT:
1. Track RESULTS
This is the most important. Go get a muscle measuring tape. They are $20 bucks at GNC. If you dont want to, go get that yellow tape measure out of your toolbox in the garage. Measure your arms, chest, triceps, waist, quads, everything at rest, and then flexed, and type it in an excel sheet ONCE A MONTH.
You can not see results in a mirror. There is nothing like eating shitty, bland food, working out, etc and then you look in the mirror after 2 months and you cant really tell any difference and then you give up. Because you've been looking at yourself everyday, you cant tell any difference. Then you'll see an old friend and theyll see wow you look great and youll say, "Really?" shit I just quit my diet 2 weeks ago.
2. Ipod, Music Player, etc
It is soooo boring going to the gym and just people watching. You need to be in the zone, you need to enjoy yourself there. Get an ipod or something and an arm band and wrap that thing around your arm and listen to some jams, cranked up loud.
3. Mix up your workouts
You cant go there and do the same routine. You will loathe going to the gym. If you do flat bench one day, as part of your chest workout. Trade it off with machine bench, pushups, whatever. Dont do the same shit.
4. Mix up your diet
add a fat burner after a few weeks
add a supplement a few weeks after that
make your diet stricter
change your meals to try something new
keep your body guessing
just because you are on a diet doesnt mean you have to eat the same shit