I am single and holiday alone - there are as people have said negative and positive aspects to it. But the alternative is to spend that week/fortnight not going on holiday and just being at home, which is surely not as appealing?
Yes, going alone means nobody to share the experience with or to talk to about what you have seen and done, but it still means you get the stimulation/ interest of a new place, different things to see and do and basically a break from routine. If the choice was go alone or not go at all I would always choose to go alone.
You can negate some of the negative aspects (like dining alone) by self-catering (eg Airbnb) and I also do the lunch at a nice restaurant and dinner in the accommodation thing. Eating alone at lunch seems much more socially acceptable and is cheaper too.
Yes, going for a drink in the evening is more difficult/awkward on your won, but on the other hand you are abroad in a place where nobody knows you, so who cares what other people think. :) Or just buy a nice bottle of wine and enjoy that in your accommodation, then do the sitting on the terrace having a meal/drink and people watching thing during the day.
If you crave some company then join an activity like a city walking tour or guided tour of an attraction. AIrbnb also has activities now, so you can go on a hike, go sailing, do a wine tasting etc without having to go on a group holiday.
I think the key is to approach it with the right attitude - focus on the positive things about a solo holiday like being able to do exactly what you want, when you want, without having to worry about what another person/people want to do or don't want to do. And reduce some of the negative aspects of it by using the tips I and others have given you here.
If you live in a big city there may also be a Meetup.com group for holidays/city breaks - that way you get to go with other people but as it's not an organised tour from a tour company you are pretty much free to do what you want while you are there or people suggest what they want to do and ask who wants to join them and you can do the same.