<div class="FTQUOTE"><begin quote><i>Originally posted by: <b>sunshine39656</b></i>
I'm always tired after working all day, but realize the need to exercise.
What's your motivation and what kind of exercising do you do? (But mostly, what's your motivation?)</end quote></div>
I know this thread is old-ish, but it's been dug up, so I will throw in my two cents. <img src="i/expressions/face-icon-small-smile.gif" border="0">
To be perfectly honest, I can summarize my motivation in three points. Keep in mind I'm a male. YMMV.
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1. I want to have some muscle on me. Out of shape dudes are treated "differently" (worse) by other males. I learned this first-hand growing up as a skinny kid.
2. I want to look attractive to the opposite sex. (Very vain, but just being honest.) The rub is I'm married. Fear of abandonment? Dunno. But there it is.
3. I - quite literally - feel depressed if I don't have endorphins (from exercising) rushing through my head at regular intervals.
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Personally, I find that weight training is very satisfying. Whatever lousy mood I may be in, it alleviates it. I don't like cardio very much, but I (and you) need it, so I do it.
As for feeling tired out at the end of the day: my observation has been that different folks have different physical peaks during the day. I actually weight train starting around 20:00. I know many people who are most successful with early morning - ~06:00 - workouts. I think they're nuts. But you have to experiment and determine what works best for you.
Above all else, proper form, pseudo-healthy diet, and <i>consistency</i> are key. Best wishes on getting started and sticking with it. It may be that you'll discover the feeling you get from it will motivate you.