This (situation of seeming helplessness) is where someone might say "nonsense -- use your will power". It is where a good motivational "coach" might somehow inject me with will power. This will generally involve telling me things I "already know" in an "inspiring" way.
What is that all about? Coaches, sales motivators, and military officers think about it all the time, as do preachers (or evangelical preachers at least?). A huge portion of their job is to "be inspiring" -- to transform the weak willed into the strong willed.
To many, and I'd guess most, of us, "will power" is elusive -- at least in some situations. For me, sometimes, wishing I had more "will power" is like having known at one time, how to wiggle my ears, but having lost the knack, and looking in the mirror, thinking about wiggling my ears -- trying to will them to wiggle, but seeing nothing happen.
Some days I make a promise, and it is a promise. It shifts my being. I keep envisioning the outcome that I promised or willed to come about, and I jump out of bed in the morning excited about doing whatever it takes to produce that outcome. At its purest, a promise isn't about a particular set of actions I will perform. Living in a promise, in its purest form, I don't know how to make it come true, but I keep coming up with new ways of doing things. It often seems like unexpected means and opportunities just "crop up".
Some days I say I will do something, and it is not a promise, but just a prediction, or some wavering hybrid of a promise and a prediction. At worst, my listening to myself may be like "yeah, right". I'm sure many people experience this when they say they are going to stick to a certain diet, or stop smoking. Sometimes I say I will do something, not in total bad faith, but I leave myself an unspoken "out", like "if I doesn't run into too many obstacles", or "I'll be there at 10:00 (unspoken: if the traffic isn't too bad)". Sometimes I am betting on myself or betting against myself, like, "I think I'm going to do it this time", or "I have this sinking feeling like I'm going to let myself down".
To observe, and make predictions about, oneself is to exit the domain in which promises live.