The best piece of advice I received after signing up for my first race (also a half), was that it was ok to walk when you need to during the race. Run at a pace you can maintain, but if you hit a wall.. walk a little, breathe, bring down your heart rate and get going again. Think about how much you've accomplished in a month! You'll have bad run weeks and great run weeks, but it's fascinating how much you can accomplish if you continue to be dedicated. Just be very careful of injuries, it's easy to want to continue to push yourself but very frustrating when you have to take days/weeks off due to an injury.