People always leave.

Why do people disappear from our lives? Its one thing for a loved one to be taken from us, or to even move away due to a job transfer, and just lose touch over time because.. well we get busy with our new lives, but for someone you care about to voluntarily disappear from you world?? And you ask "why?" but all the say is "Its whats best". Or sometimes they say nothing at all. They just disappear. And then you eventually start living your life again. Doing your day to day things, learning to live without that one person in your life. Finally start getting happy again. And then it happens.... They're back. Just like that. Why do people think they can just disappear from your life, and then walk right back in it... as if they never left in the first place. Or they know it was wrong and say "i'm sorry, I made a mistake, I missed you so much" or "I'm sorry I didn't tell you what was going on, I should've at least let you know what was going on". And why does it always seem to happen right when things are starting to go great, and you're starting to get things back on track. Is God messing with our personal lives? Cause I know, I sure didn't sign up for this. To have people I love walk in and out of my life constantly. I just got someone back, and will be leaving again soon to go to the military.. and I fear that I will lose this person again... And then another someone that I trusted disappeared from my life, with no word what so ever.. I let it go, and now this person is back. Why do people always leave!? I'm really starting to learn to not get too attached to anything these days, because nothing is ever constant. People always leave.