First of all, I think you have to stop wanting to be happy. People can't be happy all of the time, it just isn't possible. Plus, you only have to look at most of the threads in relationships to see that being in a couple often brings huge amounts of misery.
I think it is far better to look at ways to enjoy life and I say this as someone who has spent more of the last 16 years single than in a relationship.
It took me ages, but I found a sport I really enjoy and joined a club where I can do it. It was a bit of a leap of faith but I'm so glad I did it as I have something that I enjoy doing, brings me pleasure and is a bit sociable.
Job satisfaction - another area where you can find personal reward. If you can find a job that you enjoy, then you have another huge area of your life that brings you pleasure / satisfaction & enjoyment.
Friends - don't just meet them for a drink or a coffee, do stuff with them. See if they'd like to join you on your hot air balloon ride or maybe wander around a gallery or exhibition, go to the beach, try afternoon tea somewhere different, potter around your local farmers market etc. Doing things builds connections and shared adventures.
Take pleasure in the small things - watering your pot plants, watching the sun set, the smell of fresh cut grass, the first sip of an ice cold G&T or hot latte, the feeling of hot water on your back in the shower. It sounds like airy fairy new age shit, but there really is so much joy in the small things that happen around us every day.