I'm switching jobs in a few weeks and am shitting myself!

I am staying within the same company and discipline, however I am going from being a commissioning engineer who is based on the project sites to being a design engineer based in an office in Germany. There are many plus and negative points but I am pretty sure the transition from working mad hours (anything upto 100hrs a week) to normal office hours of 35 will be a huge shock to the system. No more travelling/ working in different countries, no more doing exactly as I please without anybody looking over my shoulder. On sites there is always places to hide, during quiet periods it is well acceptable to surf the net and do whatever pleases you. However I can't see that happening in an open plan office.

mmmmm, and why am I changing?? thats something I am still asking myself. The chica part of my life is the driving force I suppose.