Of all the signs, yours is the one that can afford to burn a little midnight oil. You can indulge the party mood and at the same time you'll be able to cope quite well on the work/career front too. The more you get done in the more serious first half of the month, then the more you'll be able to extract from the fun vibe in the latter half: regard it as a kind of deserved reward!
After the 16th the reliable influences will morph into inconsistent ones. This will be when you could become slightly unpredictable and fickle, and you may not be the only one to send out confusing messages. There will be two basic rules to follow in order to minimize the potential stress: one – stick to old promises and two – don't make any new ones just yet!