In my case it led to a reputation for getting things done correctly on time.
Because I'd only say yes if I actually thought it was possible - the thing I realised is that the push back on estimations is only at the start of a project, all they remember at the end is you said X, it took X.
If I could go back 20 years and talk to 20yo me this is one of the things I'd tell them.
Any level of work you put in over the minimum just becomes the new minimum.
Learning to say no and sticking to it would have dramatically improved my life (it did when I figured this out around 30).
Career has gone from strength to strength ever since.