If you're going through half or a third of a bottle a night, that's a fair bit more than a glass a night. I'd be a bit worried that you're not facing up to the actual amount you drink, which isn't a great sign.
Personally I don't think a couple of glasses a night is loads, I won't be particularly concerned about a friend who drank this amount, as long as there were a couple of days off. I'm not a doctor though.
I think you need to be careful that you don't gradually increase to a half bottle every night, which can lead to a bottle every night. I've know a few women who ended up with a bottle a night habit, and it's way too much.
I think you need to work out what exactly you're getting out of drinking. When I was in my late 20s my then flatmate and I got into the habit of having a lovely big gin and tonic when we got in from work, and after a few months realised it wasn't the best habit, so cut it back to just Fridays.
I'm single and living alone now - happily! - and I rarely drink at home because I've realised that alcohol is an enjoyable social thing for me, so very happy to open a bottle of wine when friends/ are around, but rarely do it when I'm by myself - eating chocolate has pretty much become my cosy night in treat, which has it's own health problems.
So, try to work out why you're drinking - and I write this as someone who likes drinking, likes the buzz, likes the conviviality, likes the taste, likes to split a bottle of wine with a friend.
In my case, drinking to relax after work was becoming too much of a good thing - 1 drink became 2 - but it was easy to stop because it wasn't too engrained as a habit. I think I ended up de-stressing by cooking from scratch rather than heating something up.