I suppose I would be a better singer if I had taken voice lessons. I just started singing because the singer didn't show up one night, and I wanted to get paid. I learned under fire.
I have almost always taped (now digital) myself, for more than 30 years. I am my own worst critic, but the sound has improved to the point where it's not painful to listen to.
Over the years I've learned not to hurt myself and to sing more or less on key.
I had some good encouragement from friends when I first started trying to sing. Something like, "that's not so bad, stay with it," etc. As you get experience, you learn what you can or can't (at least SHOULDN'T) do. I'm still learning to sing after all this years, and I'm lucky enough to have a few close local entertainer friends, such as Hank The Lurker, who continue to pass on their knowledge.
I can't do Piano Man, but I love the song. I can do Merle, Elvis, Conway, George Strait and others who were kind enough to sing in the correct key for me.
Most valuable advice you will ever get:
DON'T DRINK ALCOHOL WHEN YOU WORK. The doctors, lawyers, bankers, etc. don't get drunk at work (at least most of them don't) and neither should you. It doesn't make you sound better, but it can make you THINK you sound better and can make you try things you shouldn't. Also it will almost certainly shorten your career and life.
Look at me being serious.
DonM