why do people leave?

I know I have wrote about this in the past, but here I am about to do it again. Forgive me for the redundance. I feel sad right now and want to just vent. One of our good friends just called me and told me he has gotten a job offer in Iowa, that is a few states away. I didn't know what to say, I am so happy for him and I really want the best for him, but I am sad also, I just sat there and he said don't start crying because I can't handle that, I was like I won't (even though I thought about it) and he said you just have to come for week long vacations and we will make good use of e-mail. I was like yeah, you're right. it is so hard to say good-bye to people. Why does life have to change so much? There are so many people that I have had in my life for a season and then they are gone. Sometimes they come back, (sometimes years later when you least expect it) and sometimes they don't come back. And even though you meet new people and they are wonderful, it doesn't completely fill the void. It just isn't the same. I hear there is a season for everything a time and place under the sun for all things in life, it is just hard for me to say good-bye whether it is through a misunderstanding, hard or hurt feelings, job transfers, drifting apart or the cold hard reality of death. I would have to say that is one of the hardest things in my life to deal with and sometimes I wish I could crawl in a hole and pretend it isn't happening. But I can't, it is a reality and I must square my shoulders, be brave and face it. Life will go on.