If you swore to do something, you must do it.
As a person, your word is a direct reflection of your character; are you steadfast, trustworthy, and firm? or flaky, fading, and discouraging?
Therefore, when you swear to do something, swear it from your soul that that action is something that will be undertaken, it is imperative you do not corrupt your word.
If it is disciplines you swore to do every day, do those disciplines every day. You can write at midnight, dog tired, yet if that is how it is done then that is how it is done. As long as you write the truest thing you can write at midnight, simply wanting sleep, then it is okay.
If you swore to get lunch with a friend — not a measly, “oh sure, that sounds like fun,” but truly a full-hearted commitment — then you must get that lunch.
Be true to your word. And if you can not be, make sure you break your word as seldom as possible.