An alternative explanation I can think of is the placebo effect. It's possible that your behaviour Y changed after changing X, because you believed behaviour Y would change. Especially as you wanted to change those behaviours in the first place.

Also, even if this was not due to placebo effect, it's only evidence on how your mind works. Other people's minds might work differently. (And I suspect it's also quite weak as evidence goes, though I can't seem to articulate why I think so. At the very least I think you'd need a very big sample size of behaviour changes, without forgetting to consider also the failed attempts at changing your behaviour.)