Why must we be apart?

So today I had to say goodbye to people who are very near and very dear to me. This is something that has been recurring over and over on furlough, because inevitably I must return to Thailand. I know that is where I am called and where I will be for a very long time, but it causes me grief to know I have to live apart from those I love and I find myself asking God "why?" Why is it that to serve You I have to leave people behind when it feels so much more natural that we should be living life together? Why must I leave them when I feel like they need me? And I am afraid of this: At the end of my life I just don't want to find myself wishing that I had lived it more with them! And so I come to these few answers, and I don't know if any other missionary has found better ones. I give people up to God knowing that He loves them so much more than even I do, even if it feels like my heart will burst. He can also take care of them so much better than I could, even if I stayed. We also have all eternity to live together, and our short time of separation on earth is going to seem trivial to that and I must do the work that is set before me. Finally in the end, there is only this: My Lord is worth the sacrifice, but that doesn't mean that it doesn't hurt.