There's a phrase we used to use all the time when I worked in Higher Ed: if it didn't happen on paper, then it didn't happen. This extended to everything from scholarship offers to discipline hearings to program reports. As both the giver and receiver of the blunt force blow of this mentality, I know that it was not so much used to annoy the parties as it was to teach discipline and accountability.
In housing/residence life, I often had to sit with two roommates and negotiate a Nuremberg-level compromise so that they could live peacefully with one another, as one of the two ALWAYS did something that annoyed or frustrated the other.
In my spiritual - and physical - life, I find myself often telling God "Okay, I'll stop doing Y." "Okay, now I'll really stop doing Y." "Okay, this time I mean it: I'm going to quit Y now." "I really should start doing X more often." "Tomorrow, I'm going to get right on X. Promise." "Okay: now I'm really, REALLY going to stop doing Y." And so on and so on.
So, because I know me and I know that my words - while not meaningless or said in a vain or empty matter - need some kind of action to back them up, I just sat down and wrote out the prayers to God I have spoken again and again. And the sins I have asked forgiveness of again and again. And the things I know I need to do but just haven't gotten off my spiritual duff to do so yet.
Therefore - it's in writing. It happened.
And although God, in His infinite mercy and justice, does not hold me accountable for the sins I am forgiven of, I know that I hold me accountable through guilt. Through negligence. Through apathy.
So I can now, on some level, hold myself accountable.
And before anyone raises a hand and asks about an accountability partner: I find it far more difficult to lie to myself than to anyone else.