When someone with CFS/ME pushes their body beyond its limits, they suffer from an increase in symptoms known as payback. For me personally this tends to present itself as dizziness, loss of balance, feeling generally lifeless with lack of strength, fatigue and severe pain.
Sometimes payback is worth it. I had an amazing day on Saturday which was totally worth the payback I've had yesterday and today. I knew I'd get payback but sometimes you accept that as a fact and choose to have a day that you know you'll suffer for later. My choice, my body. The payback has been rather brutal though, and I'm hoping it won't drag on too much longer..
The difficult thing is knowing that probably 99% of people my age would not even have any difficulty doing what I did on Saturday. And the payback lasts so much longer than the initial exertion, which seems mightily unfair.
You also have the problem of medication side effects if you end up needing stronger pain meds because of the increase in symptoms, and then it seems almost a waste to be using pain meds to simply lie in bed dozing. I also have the issue of medication interactions now that my medication regime is getting increasingly complex.
What also makes it hard is that payback is worst in the mornings (for me anyway), so you get to the evening and think tomorrow will be ok, but then sleep is normally disturbed because you have nothing to distract from the pain and payback flares back up again in the morning. You feel much worse than expected, and the comparison with the symptoms you expected is what is difficult to tolerate.
When I've had an amazing day and knowingly pushed my limits I have no problem with being stuck in bed in the dark dozing the next day. These days I accept that, and I have learned to expect it.
The psychological pain comes when you don't seem to be coming out of the payback as expected and you fear that you may have triggered a relapse, or the payback seems worse than you anticipated or you can't get your pain even vaguely under control.
Payback is a tricky thing to get your head round, because you have to anticipate it to be able to expect and accept it. You don't know at the time what the severity of the payback will be, so you can't always judge whether doing something will be worth the payback it causes.
There's also the fear that you may be causing long-term damage by triggering payback, although no-one can know for sure at the moment whether it's a detrimental thing to do, because the mechanisms of CFS are not sufficiently understood. I trigger some degree of payback in addition to my constant symptoms most days because I am continuing with my studies and I have continued without any real adjustments so far (although this is currently being discussed and I am finally looking at ways to reduce the strain on my body). I don't see the point in constantly avoiding causing payback at the expense of quality of life though. Personally I don't see the point in constantly living within my limits in order to get my symptoms as low as possible, because I would simply have no life. Yes, some would see this as being reckless with my health, but it isn't really- no doctor has ever said that what I'm doing is wrong or dangerous and they have been supportive of my mindset. When I walk too far and injure myself it clearly is a stupid thing to do and isn't good for my health, but the day-to-day pushing of my limits isn't as clear-cut. Yep, it probably has caused a worsening of my condition over time, but that wasn't necessarily going to be my body's reaction to it, and without trying I wouldn't know what my body could and couldn't cope with. To know your true limits, you've got to test them.
I'm not saying that my approach to my illness would be right for everyone, but it's the way I chose to deal with it. I might need to change my approach and pander to my illness more in the future, given that my condition is deteriorating, but I am looking into ways to make life more manageable and will be responding appropriately, so I'm not mindless with my illness, I just choose to have a life sometimes, and suffer the consequences.