We are Forerunners. Guardians of all that exists. The roots of the Galaxy have grown deep under our careful tending. Where there is life, the wisdom of our countless generations has saturated the soil. Our strength is a luminous sun, towards which all intelligence blossoms... And the impervious shelter beneath which it has prospered.
The absolute worst thing about coming back from a vacation is that, for the time that you're away, your normal training regimen and fitness routine is completely disrupted. Trying to pick it up again is not a pleasant experience.
When you're on vacation, by definition you aren't lifting heavy weights or going on long runs or doing intense martial arts training. (Well... we were, for the first few days, but that's another story.) If you are, your idea of a vacation is probably quite different, and a lot less fun, than what most people have in mind.
As a result, your muscles lose a small amount of definition and strength because they're just not being forced to do very much work.
The overall loss in strength is actually not that severe- if you were strong before you went on vacation, you're still going to be strong when you come back. The difference is that stresses that your muscles would normally adapt to without the slightest hesitation suddenly become quite difficult, even dangerous, when you have to resume training. Your muscles will have lost a degree of flexibility, strength, and work capacity through inactivity.
It is also possible to lose weight during a vacation- and for a powerlifter, after a certain point, this is not a good thing. My tennis partner asked me yesterday if I'd lost weight; I told him that I hoped not. Unfortunately, he was right- my lifting belt was rather more loose on me today than I reckon it should be. At some point, a powerlifter will have lost pretty much all the fat he's ever going to lose, so losing weight means losing muscle, and that is NOT good news.
All of this means that when you step back into the squat rack after a vacation of decent length, well, it's going to suck.
I won't bore you with full details of my workout today. Let's just say that normally on a Sunday I would be trying to maximise my 1RM number for squats, deadlifts, and overhead presses. That usually means work sets for squats starting at 335lbs and continuing on to 365lbs if I can. When I'm in good condition, that sort of workout is hard but routine. At peak strength I am fully capable of repping out 315lbs squats.
So you can imagine how annoying it is to come back from an amazing and life-changing vacation and discover that squatting 315lbs suddenly became ridiculously hard. It's like I'd completely forgotten how to do squats over the space of two weeks.
At least my deadlifts hadn't suffered too much. Squats are a very technical and difficult exercise- at least for me- but deadlifts are not. They are also my absolute favourite exercise in the gym, so it would have really sucked if I hadn't been able to lift 405lbs for reps. Fortunately that didn't happen.
The thing is, the longer you delay getting back in the saddle, the more painful it's going to be down the line to do so. At some point you'll give up entirely and not bother, and then all of your gains will go to the place where CrossFitters give themselves hernias and rhabdo.
To be clear, vacations are a Very Good Thing from a training perspective- you can come back even stronger from a couple of weeks off, provided that you get back to training. The suck comes from the fact that for the first few workouts, your muscles will be sore as hell and you'll wonder where all of your gains went while your body re-adjusts to the demands you're placing on it again.
All of this applies to much more than powerlifting, of course. Ask Carey about how his playing sounds after a week away from the fretboard, and he'll probably tell you just how much it sucks having to get all of the calluses back and getting back into practice. This applies to any aspect of your life where you've built up a solid routine, abandoned it for a couple of weeks to do something different, and then come back and wondered why the hell everything seems so much harder.
The only way forward is to embrace the suck. Do the damn work. It will get easier after a week, maybe two. And then you'll break through the barriers of pain and frustration that were holding you back, and you'll hit new personal bests.
That is the benefit of going on vacation once in a while. The drawbacks are the price that you have to pay for those benefits. That's all there is to it.