Biggest mistake I may have ever made was NOT listening to my shop teacher in HS. He wanted me to stick with machine work, but I went to the auto body shops instead. Kicked myself in the butt for 50 yrs now for not listening to him.
I have always liked the "older" type stuff and machine tools are some of the best. Like Scuba says, ya have to use that thing betwix your ears a lot more. I have known a few very good machinists and all of them can show ya ways of doing stuff most others would never think of.
I ran manual lathes and mills for years and it was awesome, truly a passion that I got paid for. I ran some parts metal to metal, 0 tolerance. Then when asked to run CNC's I was scared to death. But I did it, I learned G code, got to writing my own programs and enjoyed it very much. I got to love the CNC machining but the manual machining is where it's at. Still have scars from chips lol.