OP, I used to work with someone who met her drop dead gorgeous hubby a couple of years after she retired at 63!! Not saying that you will have to wait that long, but just to assure you that it happens. She was single all her life, lived with her single sister, and was a slightly eccentric lady filling her time with odd, but harmless hobbies. She didn't follow the crowd, but was true to herself and her interests.
Then she retired, only to reappear at a works do a couple of years later, looking tanned and glamorous, just having returned from a long cruise with her silver haired and very distinguished hubby, who obviously adored her.
It was quite an entrance!
Nursing is hard because of the shift work, meaning that it is hard to settle into a regular social life and activities. Single life is hard too - I married late and was sooooo chuffed to have someone to put out the bins!! They were the straw that broke my single back everytime. It was a joy to be able to share that task!
You do sound exhausted. Do you manage to get to go away on holiday? Could you book yourself a weekend away or even a day away, as a Christmas treat, and pamper yourself. If you were in a relationship, you would spend time and money on the other person, to keep them feeling good, so do invest some of that time and money in looking after yourself, and think about how life now can be better for you. You deserve it.
(Married life with the wrong person can also be heartbreakingly hard, and the facebook pictures never tell the whole truth - in fact those who post about how happy they are are often trying to convince themselves. )