Complicated situation with a younger guy
Sorry for the super long story...
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I'm a 27 year old graduate student and I briefly met a 21 year old guy about 2 years ago. We have been been talking over facebook and email and texted. Our friendship developed quickly and I can tell there were some emotional attachments formed between the both of us. He'd check on me to see if I've arrived from my flight to my meeting safely, what I've done on a daily basis, etc. Our communication had really taken off. I found out that he had been dating a sociopath prior, and she was slowly trying to weasel her way back into his life again. He was distraught but didn't know how to deal with it, as she uses emotions to guilt him into talking to her like "you're the only friend I have" etc. And he sought comfort from me. I walked him out of the situation by talking to him for hours and explaining to him what she did was pure betrayal and that if he continues to talk to her, his relationship with his family might be ruined. It was a very emotional experience because he was young and she was much older (lied about her age) and manipulative. He finally saw things clearly after I've emotionally supported him for a good 2 weeks or so. When this was all over, I felt extremely exhausted and full of anxiety. I felt like it wasn't my place to be responsible for the action of a young guy, even though I was very much attracted to him and vice versa. So I told him to let's not talk for a while because I needed a break for this craziness. He pleaded for me to not leave him and I said I couldn't offer much of anything right now and really need my time so I left.
Three months later, I felt very guilty for abandoning him when he was emotionally weak so I initiated conversation again to say hello. He seemed kind of cold and numb. Our exchanges didn't go very far. It felt as though he wanted me in his life, but he wasn't willing to be more open with his feelings and I didn't want to force a friendship out of him, so I asked whether he wants me to leave him alone. He got extremely angry and said "leave. That's what you do best, isn't it?" And I explained myself again that I didn't leave because I didn't care about him, but it's because I was mentally exhausted trying to get him out of an awful situation that was about to suck him back in again. He said "STOP bringing up the past. I want nothing to do with it now." So I left him alone, not really expecting him to talk to me ever again.
About 6 months later, he initiated contact with me, starting with small talk, asking how my grad school is going. All the small talk aside, things started to get close and personal again. We'd talk daily, And things eventually turned somewhat sexual. We both found each other very attractive and sent each other pictures of what we wore for the day as we were getting ready in the morning, what we ate, etc. It's as though we were right next to each other, even though we were a few hundred miles apart. He told me he fantasizes about me and think about us meeting up and going out on a date and seeing how we are with each other. We made plans here and there but never carried it out because we live a few hours away and we are both in grad school. Eventually I started getting anxiety over this again. I realized that he is volatile, passionate, but much younger nonetheless, and I couldn't really date him in reality. So I thought it was pointless to keep each other led on and hooked. I talked with him about going separate ways so we can get on with our real lives. He was furious but I thought it was for the best for both of us. It was painful leaving him like that. Again, he didn't want to part ways and we left it on pretty bad terms. We couldn't keep a friendship going without it getting out of control and romantically involved. Meanwhile this has been going on and on, neither of us dated in real life.
Then 3 months later. I started getting really bad anxiety over my career and (he's in a similar field) I felt like I had no one to talk to. I felt kind of desperate and contacted him to talk. He gave me a little comfort here but overall, was very cold. And I understand why he would be. I said I felt bad for what had happened between us and that if we want to continue being friends, we'd have to set some boundaries. He said he didn't want any boundaries. We fought over this again, and I said I really can't do this and left him again. He was very cold this time, and I really was not expecting him to ever want to speak to me again. I said why don't we delete each others' contact and never do this again.
About 2 months later, just very recently, he contacted me out of the blue. He wrote me and asked how I was doing. Some small talk was exchanged, he told me he missed me a lot. This time, he was a lot more sentimental and emotional with his words. He said he really wanted to see me this summer. I'm on break from grad school for a few weeks, and he asked me to visit him (since I have family living in his city and I myself plan on applying for residency there), or he can take a train and visit me. He said he really wanted to see me this summer. We made plans again, because we both think about being together in real life and seeing how things go. But I am much older, and I would prefer a stable and serious relationship at this point in my life. I know physically we both want each other, and there's obvious emotional attachment after hanging around on and off like this for 1.5 years at this point. I got cold feet because I worry if we like each other a lot, we'd have to do long distance, and seeing how unstable things were, I thought it may become a vicious cycle again, and it's really tough for my studies and his. He got extremely angry this time when I got cold feet. I don't think I've ever seen this many angry words thrown at me via email. So I wrote him a goodbye letter right before he went to travel outside the country. I said that I think he's very intelligent and I enjoyed his company, but we have different needs due to our age differences, and that I hope he can find a girl on the same page as him closer to where he lives. And I thought my email was clear and sincere.
Three days later, he's abroad traveling, and he wrote me "greetings from the other side of the world." I know he read my goodbye letter. I was a little shocked and didn't expect him to contact me. What I don't understand is why he'd do this after things clearly haven't worked out after this vicious cycle of talk, not talk, repeat. I said "Did you read the letter I sent you?" He said "yes, but it was during finals, so I didn't get a chance to reread it yet." And I just cut the conversation short and said "have a nice trip" before I said anything I regret.
I'm just trying to understand why he would still contact me after all that, and I want to decide what to do and go with it this summer. I really don't want to drag this out any longer. Any insight is appreciated. I'm sorry for the lengthy post.