I always feel so exhausted after my morning dancercise

I do it way early in the morning for about 20-30 minutes, usually. Once I finish, I shower and get ready for my day and all that, but when I sit back down, it all suddenly weighs down on me and I need to rest again. It's gotten to where I've actually fallen back to sleep! I've noticed this started happening since that day a couple weeks back where I did a combined time for 90 minutes of dancercising throughout the day, only to find I overdid it and felt very exhausted the following day. Perhaps my body is still exhausted from that somehow so that whenever I do it again, that's when it hits. Not sure if that's how it work, but that's when I've noticed this happening...