Dude, I sing like a frickin' bullfrog, but you know what? It's my voice, this is how I sound, and I can't sound like anybody else. And it took a LOT of people telling me that before I accepted me as me. I looked all through Real Band and there isn't a Sinatra plugin.

Write in a key you can sing comfortably. Write in a way that you don't have to try and hold out tied whole notes for 29 bars to where you run out of air. Mainly, DO NOT be tentative. When you hold back, you WILL be flat. Send it out to the back row.

I can only use myself as an example because I have never been anybody else. I retired on New Years Eve when 93 turned into 94. At that point I was the 2nd singer in my band so I sang a lot. 1/4 of the leads and harmony all night long. I could sing then. In the 15 years I was out of it, I did not even sing in the shower, and I lost it. The vocal cords are a muscle like any other muscle and need to be used. Just sing as much as you can, focus on your breathing, sing as much as you can, make sure you sing from the diaphragm and not the throat, and sing as much as you can. Also, sing as much as you can.....

And NEVER be timid about your voice. NEVER. Stay within yourself and you'll be fine.

Edited to add this PS.

This is already a Daryl Hall, and there was already a Freddie Mercury (the 2 male vocalists I hold in THE highest esteem). Now you be you.