And pack extra food! I've found that since I've started commuting 3-5 days a week to work I'm hungry ALL THE TIME! My dinky little sandwiches don't cut it any more so I've been stocking up on snacks like nuts and hard-boiled eggs so that I can avoid an extra money-wasting trip to the cafeteria.

Also, I think transitbiker hit the nail on the head. One of the most enjoyable aspects of cycling to me feeling myself improve. It just starts feeling easier after a while, especially if you're not "training" or looking to improve your speed. I do an 8 mile round trip with a decent amount of elevation that used to get me into work sweaty as all heck. Now, even though it's warming up, I'm much more comfortable (and less gross) when I get in. I typically keep the same pace (~15 mph for the trip), but feel less tired every week than I did the week before.