In my experience, meditation helps make one more mindful throughout the day. But relying on the momentum of practice only goes so far.
Mindfulness is one of the few things we non-arahants can never do enough of, as long as one isn't neglecting taking care of oneself and others. In fact, if it was all one did, one would be assured of arahantship or non-returning within seven years (MN 10). But even a single moment of mindfulness, restraint, metta, or any other wonderful Dhamma teaching-in-action is another drop in the good bucket.
Think not lightly of good, saying, "It will not come to me." Drop by drop is the water pot filled. Likewise, the wise man, gathering it little by little, fills himself with good.
When this is, that is.
From the arising of this comes the arising of that.
When this isn't, that isn't.
From the cessation of this comes the cessation of that.-SN 12.61Ex nihilo nihil fit.