I have the same problem and had to give a pitch for work yesterday (with colleagues, but if anything that made me more anxious because I worried about making an idiot out of myself in front of them).
Try to break the day down into small steps, so it doesn't feel so overwhelming. Focus on the travel first, you may not like doing it but you have done it before so you know what you are doing. Given the chance I always leave lots of time because the thought of being late make me really anxious. It also give a little time to recover from the travelling part and prepare for the presentation part.
If you are using slides, try to really plan what you are going to say especially for the first couple of slides. I generally find that getting started is the worst part and then once I get into it, it gets easier.

Maybe also give yourself something to look forward to as a reward to yourself for getting through the day.
Sorry, this is probably not much help but if I knew the answers I wouldn't have been such a nervous wreck yesterday

Good luck and hope it all goes well!