The cinema is still seen as being a 'date location' and I do wonder why there should be a stigma attached to watching films in the cinema alone. The whole experience relies on silence and concentration, assuming one is beyond the age where the 'date' merely involves necking in the back row of Lethal Weapon 3. Nevertheless, I always feel a pang of shame when I request my single ticket, and tend to put the word 'just' in front of my ticket order each time. This is odd; the films I watch solo tend to be in the afternoon, and the vast majority of other paying customers have gone solo too - there's solidarity in numbers for you. You certainly get a varied crowd, with the oddest set of creatures being discovered at the Ritzy for 'Bobby Fischer against the World'; I guess there aren't that many fans of chess in Brixton. I did rather pity the soul who turned up solo to watch 'Antichrist', though maybe the embarrassment of watching genital mutilation with a friend outweighs the embarrassment of having the rest of the cinema think you're really into that kind of stuff.
The rules of eating out seem to be that it's an activity best done with friends, family or a partner and never alone. This is not something I agree with. Eating out alone, particularly at lunch, feels rather decadent - it's something that Gatsby might do. You get to order exactly what you want, your wine choice always complements your food (not someone else's) and in between courses you get to read a book (be honest, on some dining occasions it would be great to be able to get out the book even when not going solo). If you should feel embarrassed when dining alone, all you need to do is take a notepad and pencil along with you. At various stages you should sniff what's on the end of the fork and take long lingering looks around the dining room. Maybe order two starters and ask the waiter for a cleaner knife. If you go to all this trouble, you might convince people that you're a food critic simply doing his or her day job.
One should not be afraid of holidaying alone, but it is worth bearing in mind two simple rules. Firstly, go to the US, where your accent will be enough to gather together a whole set of new chums on day one (disclaimer: this will not work in Boston, where you are still regarded as the hated oppressor). Secondly, you can make the practice sound less weird by simply describing your holiday as 'travelling' (note that though there's no set definition for this term you're unlikely to convince many people that a long weekend in Dublin is a valid use of the word).
Sorry, I can't do anything for you if you have the desire to sit alone in the pub. That's just weird and you should be ashamed of yourself. Freak.