If it's just hit you then take today to grieve then tomorrow start to focus on what you do have and could still work towards.
Today make a list of everything you feel you've missed the boat on, drink hot chocolate, eat biscuits, watch sad films in your jogging trousers and old t shirt or whatever - as allow yourself to feel sorry for yourself.
Tomorrow make one page with a list of all the good things in your life - even tiny things, like lie ins and wine and chocolate and your favourite books/ films/ hobbies no matter how ordinary, a nice sofa or favourite pair of shoes, and big things like a good friend or close family member.
Then make a page with all your wishes and dreams, big and small, even crazy unachievable ones as well as tiny silly ones. Then pick one or two you could achieve, even if they're small things (a pet, even if it's a rat or a hamster because a dog is not realistic, for example, or treating yourself to a specific decadent item of clothing, and plan how to work towards them even if it'll take a while (eg by saving all your 20p coins or £3 a week if money is tight).
It helps to feel in control rather than wallow indefinitely.
You can go on holiday alone - travelling is more rewarding alone imo. But if it's not what you want then you haven't missed out!