I just meditated for the first time yesterday and I'm not sure if I got into meditative state or fell asleep in the middle of it; all I know is that nearly an hour went missing from my time and I was drowsy when I "came to"(for lack of a better phrase). Afterwards, I took a nap, but I wanted to know if it's normal to accidentally fall asleep during meditation, especially the first few times. Also, as part of the early part of my meditation, I focused on a happy thought for a short while, that happy thought was my boyfriend, and my heart rate sped up noticeably; I could really feel my heart moving fast and hard. Is this a normal early meditation thing or was it just what I was thinking about that caused this? Don't worry, I didn't have a heart attack or anything, but once I moved on to focusing on breathing instead of my boyfriend, my heart started to slow after a bit. A little after this is when I opened my eyes and realized I had no memory of the past hour. Is any of this normal? Can anyone help me to somehow explain some of this or just give me a new perspective?
It's not unusual at all to fall asleep during meditation as your body becomes completely relaxed. That's why it is generally recommended that you sit to meditate rather than lying down as there is somewhat less chance of falling asleep.
And yes, the changes in your heart rhythm are perfectly normal as well.