[staysaasy]

In my (admittedly limited) experience, Very Successful People say versions of "that will be really hard" very often, and say "that is impossible / won't work" effectively never.

I'm not sure if this is causation or correlation, or even which direction a possible causative link would flow in (eg being positive + open-minded makes you more successful vs. being successful makes you more positive + open-minded). But it's absolutely a pattern that I've noticed.