It's kind of a blurry photo, so it's hard to see how stressed the plant is. If it's a little shriveled, giving it a drink like you mentioned will probably help. I would maybe reduce the number of hours it's getting light- 14 hours is an awfully long time for this time of year. Most cacti are dormant in winter, so they don't need as much light (or water). That might be why it's stressed. Best of luck to you.

cd

Its the middle of winter. Do you have winter where you are? I wouldn't try poking it into growth at this time, more than likely you'll just kill it. They can get a lot more shrunken than that before there is any permanent damage, and will plump up very quickly (sometimes too quickly!) once they feel that it is the growing season. Wait for spring, keep it somewhere fairly cool (cool for indoors) and dry. You might want to have a look to see if the roots are OK before you go mad with watering in spring.

I will give my Goats Horn some time to rest. For me too its the middle of winter. For most of my plants though it is more as it is in Madagascar but drier. I have many plant family's in a basement room under controlled conditions. My Madagascar Palm and Anadenanthera trees are from a Southern hemisphere.

It looks OK from what I can see. The pot looks a bit large for it, but I've read they don't like transplanting, so leave it as is, and try not to overwater. I agree with the others - don't water it at all for the winter, don't fertilize it at all, and if possible, keep it cool (but no frost to be safe). Gradually increase light and water levels in the spring, and keep it outside during the frost free months where you live.