the biggest motivator for me, and the main thing that gets me up at 5:30am is 'will i lift heavier today? will the circuit be easier for me today? will i sweat as much as i did last time today?' the weight loss has been SO slow for me, that i'm now viewing it as a casual by-product of my interest in crossfit and weight training. i mean, i'm coming up on a year, and 10 kilos... clearly the scales aren't a positive motivator for me!
consequently, we work on 5 x 5's for most major compound exercises with heavy weights (deads, press, romainians, rack pulls, squats) and tend only to do more reps when we are doing more cardio oriented work (kettle circuit, for example). we do testing, and weekly increases in weights (even if as little as 2.5kg).
i find this works well for me