What do you mean, don't make plans?

Not doing planB means "not being pushed around by others, not being a spare tire".

PIanB is plan B, which is a backup plan to do one thing. The implication is that B is not as good as A, but if Plan A cannot be implemented or unexpectedly terminated, Plan B, that is, the spare tire, will be used at this time.

The spare tire was originally an insurance scheme for one thing, but it was given to body double and the candidate in the relationship. Whether it is career or love, everyone pursues the best and is unique, so it is an insult to be regarded as a spare tire, so there is a stalk of "not doing planB".