There may be a confusion about what "too pessimistic" means. Sometimes it means "you're incorrectly predicting worse average/median outcomes than is true", but FAR more often it means "the accuracy of the prediction is irrelevant; you'll be happier (and the advice-giver will be happier with you) if you focus more on positive than on negative possibilities".
For a whole lot of things, especially around social interactions and semi-legible cooperation, one gets better outcomes by expressing more confidence than is justified. Some of us can compartmentalize well, so we can have private estimates and preparations for a wider range of possibilities than we show publicly. Some of us have trouble with that, and are probably well-served with a touch of self-deception toward the positive side of the distribution.
Sometimes it means "you're incorrectly predicting worse average/median outcomes than is true"
That is the sense it is being used in though. What is it about my post that caused you to assume otherwise? And, how can I determine if my predictions are biased to be worse than the truth, and by what degree?
I’ve been told a number of times that I’m too pessimistic about personal outcomes but I feel like I’m realist. So I’d like to test and measure it.
This post on Overconfident Pessimism appears to cover a lot of the same ground and certainly has illuminated for me the way that I become pessimistic or give low probability to tasks or processes I don't yet understand how to do. However the article is chiefly about making predictions about innovation and technological advances, not things in the personal realm.
The problem appears to be predicting where one's own behaviour is involved (although that didn't stop Wilbur Wright).
Never the less, surely if I make a raft of predictions, assign how confident I am in each of them and it turns out I am overwhelmingly overconfidently pessimistic, then it would confirm the "I am a pessimistic hypothesis" and vice versa for someone who is considered to be too optimistic, right?