Certain things would have to occur to you deep-down before you can actually do teshuva. Otherwise you’d only be going through the motions or setting out to please others.
First, it would have to be clear to you that you’d in fact done something wrong. Now, that’s easy enough to determine within the mitzvah-system, once you know what’s right and what wrong. But then it has to occur to you that the wrong you did actually mattered, which goes deeper yet, since it touches on your view of the mitzvah-system in the grand scheme of things. If you depend on it as a marker of your spiritual standing, you’ll obviously be very concerned about having violated it and diminished yourself along the way, and you’ll indeed be moved to teshuva.
You’d then have to realize that there’ll be consequences to what you did, which is always true (after all, doesn’t every page turned affect the ones before and after it somehow, as well as the reader himself?) — and that your spiritual standing will be altered accordingly.
The next thing to ponder would be the fact that *nothing* we do is ever shrugged off as inconsequential; everything we do, good and bad, is “recorded in a book” (i.e., noted in Heaven, marked down, and kept).
You’d then do well to realize that there’s indeed a solution to your predicament now, which is teshuva. And that it’s the only solution at that. It would do you no good to simply pine away at your misdeeds, for example, or to fast; and it certainly wouldn’t help to flagellate yourself — mentally or physically. It has to occur to you that the same G-d Almighty who ordained the things we’re to do to get close to Him, the mitzvot, provided us with the means of rectifying our misdeeds and getting close to Him again.
It would then help to realize how much you’d have lost in your relationship to G-d (and to others you’d hurt, as well) by your sin, to set it against the satisfaction you’d gotten from the sin, and to realize how “expensive” it turned out to be in the end (see Pirke Avos 2:1).
And lastly, it should be crystal clear to you by this point that you’d been wrong, that you no longer want to be, and that it’s time to engage in teshuva indeed. But, what in fact are you to do to achieve true teshuva? We’ll discover that next time.