I relate, man.

The first time I smoked I was already a little nervous. Little did I know that I was about to smoke some good shit ontop of that. I was taking huge rips off a blunt. I walk inside, still doin' good, I feel a little floaty, but nothing bad. I start walking into the kitchen without realizing it, then like you said, reality sank it all at once and I started freaking out. I spent about an hour in the corner of the bathroom thinking I was going to throw up. Every time I blinked, it felt like I was waking up from a dream.

How'd I get over it? First, I figured out my problems. I remembered time was moving by really slow for me. This told me that I was thinking at about a million miles an hour. Another thing was that I was worrying about little things. My heart was racing, I was breathing quick, etc. I was letting every thing that I noticed stack on top of each other until I had so much anxiety built up I had a panic attack.

Second, I learned a bit of breathing technique. Slow, steady inhale. Slow, steady exhale. After about four times of that my heart rate is cut in half and I instantly feel better.

Taking all that I learned, next time I went to smoke I was of course nervous. I did that breathing technique and calmed myself down. Rather then sit around like I did last time, I kept myself occupied. I watched a bit of Anchorman, then went to the movies with a few friends. At the end of it all, I had a great time.

Hope this might help you.