Back to Fitness After a Long Vacation

So, after a long vacation, I returned back to working out hardcore at the beginning of this week. I completed the first day of the 5-day Challenge for Busy People, and I've gotta say...

I was SO sore! And am still sore it hurts to walk up and down the stairs 😱

I actually had to take a day in between day 1 and 2 because I was so sore. I was not expecting it, to say the least. I also noticed that I got really worn out really fast.

I was on vacation for a month amd wasn't exactly idle everyday. I did a large amount of walking and surfing. I guess I didn't use too much muscle though during that break 😝

Any tips on getting back to fitness and pressing through the first couple of tough weeks?

Edited