Early in my career I thought an estimate should be my guess of the most-likely completion time. Trouble was, if I got those estimates right, it meant I was late

Early in my career I thought an estimate should be my guess of the most-likely completion time. Trouble was, if I got those estimates right, it meant I was late half the time, and management hated that. And they kinda had a point. They were making promises to customers. They looked bad if we were late. So after a few years I started giving estimates that I was at least 90% likely to meet. And, as you say, I committed to them. In the minority of cases when I ended up on the bad tail of the bell curve, I worked extra to meet my commitment. Management was much happier. In compensation for those occasional bursts of extra work, on average I had some free time. I used that time to learn stuff, or clean up code, or automate some of my work. That made my work easier, allowing me to shorten my estimates while still maintaining the 90% rule.