First of all, know that you are not alone. I certainly have done this same thing. I had not dated for quite awhile after my divorce and at a certain point I thought I was ready. I quickly found out I was not, when I did the same thing…went for coffee and enjoyed my time with the guy and then very quickly starting thinking long term (in my mind, luckily not in conversation) and was wondering why I was only getting simple replies periodically from him.
Basically, this was such a great thing for me to learn. I discovered that I was enamored with the "idea" of having a relationship again and so I began to race ahead with my thoughts and over analyze things (as BlossomingLen shared above) and I think I was trying to get myself back into the level of relationship I had previously had…already after one cup of coffee (actually, I had hot chocolate, ha ha). I think it's very natural and fine to do that.
The good news is that you are aware of this (I was not really at the time I did this) and you want to try to look at it objectively. Good for you!
However, the guy I was communicating with was able to share with me that he really enjoyed my company but he was not in a position to be in a relationship because he is caring for his twenty-two year old daughter and his one year old grandchild and he works 10 hours a day and lives an hour away and he comes out my way to go to church 2 times a week and only is able to get together periodically for short amounts of time right now. This ended up being GREAT for me, because I realized I was NOT ready to date and I have gained a nice, STRICTLY platonic male friend (which was something I really needed). No pressure or anything.
I know I need to not think about "is this guy the one?" when I start to date again and I am working on shifting my perspective and expectations for when I am ready (I still have quite a ways to go).
If you can enjoy the times you have with this guy and the receive the communications from him as "enough" for now, without worrying so quickly about "Is this guy the one?" you will likely be able to develop a friendship with this person. And possibly more in the future, but you don't have to worry about that now. If these worries are clouding your ability to enjoy your time with this person, then I would say you possibly might not be ready to date yet right now.
Good luck!!