Ask most people what would count as success and they go vague — bigger, further, more. Vagueness is comfortable, because nothing vague can ever be missed.
It is also useless as a target. You cannot notice an opportunity you have never described to yourself.
Someone who wants something better walks straight past it. Someone who wants to be running a team of four by spring hears it mentioned at a leaving do and stays for the second half of that conversation.
Naming it costs you the safety of never being wrong. That is the price, and it is very nearly the whole cost.