Keeping in Touch?

Today, I sent out two emails to old friends that I haven't heard from in the longest time...I do this once every two/three months or so. The hardest part is that I NEVER heard back from them. EVER. It's frustrating, because I really miss them, but I feel like they don't care enough to respond, since its been at least two years since I've heard from either of them. I know I shouldn't be petty about this, so I just keep on emailing them. Do you think I should just give up?

One is my friend from fencing club. He was going through a really rough time in his life, and more than anything, I wanted to be there for him. I had the biggest crush on him when we were still in contact, and I even asked him to go to prom with me. Things fell apart, and not only could he not go to prom with me, but he transferred at the end of the school year. I called him once, in the summer, and he said he was in school and had to go. He was supposed to call me back, and I never heard from him. I'd love to call him, but I'm scared to, because I don't even know what I would say to him.

The other friend went to high school with me. We hung out in the same group and had a lot in common. However, she went off to med school, and disappeared from the face of the earth. Even her closest friends have not heard much from her, and in general, we've all given up. I used to send her letters at college, but stopped when I never heard from her.

So, what do you guys think? What should I do?