waiting on my world to change

I have about 3 weeks left in my firm. People are asking how I am feeling, and whether I am excited about my new job (starting in about 5 weeks). How do I explain this? How can I be excited about leaving a place that's basically my home for the last 2 years, where I spend 11 hours a day at least, and still, by choice, hang out with the people there after hours? That I don't really feel like I have a choice about leaving, and the situation was made difficult by things beyond my control, but that I still don't hold any ill will over anyone there? That I hope I can go back there some day, but not make that sound pathetic?

There is a new and exciting job waiting for me in September, but I fear that's all it will be - a job. It wouldn't be like this; something that I define my very self by. It just won't be the same.