You should do some practicing on the weekends (try the round trip out once or twice on practice runs).

But in general, I'd say let your 1st ride (and your 2nd, and your 3rd, and ...) shape you up instead of the other way around.

(also, if you're new to commuting, I'd do a bit of reading on how to ride safely (with traffic, not in the door zone, etc.) and make sure you have the proper equipment (helmet, lights if you ride at night))