Hmm. I am married. But my anut has been single most of her life and she is very happy. But people who are alone there whole life wouldnt know what they are missing out on so therefore thinking they are truly happy. Honestly, you will have to answer that on your own. You might be truly happy or you might be wanting someone.
Yes, I had an aunt and she was perfectly happy to be alone. She could have had a husband but she choose not to. I also had an aunt that was perfectly miserable her whole life because she was alone. They were sisters and so different.
Yes, it's possible to be single and happy. Your status whether single or married will make you happy, that happens inside when you become content in life. Engaging with other people and doing things that are easier for singles to accomplish make life enjoyable.