Step1
First off, the holidays is only two weeks of time. For me, anyway that's about the time that I find difficult to stick to my program. I run three times a week, so for around two weeks I am travelling and busy, busy, so it's hard to stick to my exercise program. So how do I do it without damaging my fitness level?
Step2
You need to know that for a short-time period, only doing 1/3 of your fitness routine will maintain your fitness level. So that means I only need to run once a week to keep my level up during the holidays.
Or if you lift weights 4 times a week, than you only need to do it, one and a half times a week.
So by cutting your time to 1/3 that should make it a lot easier.
Step3
Also, if you can't get out to run, take longer walks, or get your exercise in anyway you can. Lots of us are busy shopping this time of year, have you ever noticed how tired you are from a long day of shopping? Think about how far you've walked, how many times you've walked up and down the mall? You are getting exercise doing that.
Step4
Also if you are away, try going for walks after dinner, or in the mornings. See if you can get other family members to go with you. Than you are killing two birds with one stone. Not only are you exercising, but you are spending time.
For me, because I have a dog, this makes it easy to go for walks. I just tell everyone I have to walk the dog, and they might come with me, or they might not. This also helps the dog get away from all the hustle and bustle and relax.
Step5
Either way, do what you can and try not to stress out. Remember it's only a short time period. Once the New Year comes, get back out there. Because by not getting back to your normal routine, that's where you are doing the damage.
Good luck and Happy Holidays.
Enthusiast 
