When I get lost!!!

I don’t know why this happens to me, one thing is I love to dream, along a conversation when something that I knew always is told by the person whom I am talking to, I just transport myself to another world. Completely forgetting the fact that I am actually talking to someone. I am lost half the time in a day. Call it lack of concentration or whatever, but when I get lost that’s when I realise how beautiful life is. Recently my close friend was telling me something about work, initially I was following what he was saying, suddenly something, very personal, came to my mind, I was like…. Couldn’t register a word of what he was talking, but the shrewd guy, without taking offence to my change, just said I know you are in some other world. I felt bad, not that I didn’t want to listen, but it just happens to me very often. In fact as I am typing I am thinking about something else.
Why am I preoccupied all the time, various thought process occur, hits my head so hard that I can’t stop thinking all of it. To me dreaming is one way to relax my stressed mind, post dreaming I feel I have started something afresh, seriously, not exaggerating at all. But I have to make sure that whoever I am talking to does not mistake me.
Similarly I run short of words when I meet a friend after a long time, will not know what to ask, how to begin a conversation, funniest part is we would have had enjoyable moments when we were together, friends become strangers. I was asking my husband does these things happen, he was like… what did you say sweetheart, now I realise how irritating it can be if someone is not listening.