How can we (or I?) motivate ourselves to do things that we do not want to do?
Seems to me that "instrumental" and "punitive" approaches have been most popular over the years. Which is to say, under the instrumental approach we think, "X is unpleasant, but I need to accomplish/tolerate X in order to achieve Y, which I do desire", and thence derives motivation to do X.
The punitive approach--maybe it should be called the "threat of punishment" approach, but that just sounds long and awkward--is more along the lines of, "Q is unpleasant; but Z is even more unpleasant than Q, and Z will happen if I do not do Q".
Actually, these are analogous (although not perfectly so) to modus ponens and modus tollens, like so:
X->YFrom a motivational standpoint, one looks toward the conclusion for a desired outcome. In the first case, we want Y to happen, and we know that one of the ways to effect Y is to do X. That is, if we do X, unpleasant though it may be, we will be rewarded with Y.
Similarly, in the second case Z is even more odious than Q, but we know that if Z is going to happen, it must be in Q's absence. Thus, we can prevent Z from happening (effect ~Z) by doing Q.
These also (unsurprisingly) map pretty handily onto the psychological principles of operant conditioning: what I've called the "instrumental approach" (modus ponens) is analogous to positive reinforcement and positive punishment, and the "punitive approach" (modus tollens) to negative reinforcement and negative punishment.
All four approaches are logically equivalent, depending on how we choose our premises. It is worthwhile to note, however, that they are not psychologically equivalent--and that people may react better to what they understand as a positive stimulus versus a negative stimulus, etc.