Let’s reflect now on some of the things that keep us back from doing teshuva. We’ve already cited a few in passing when we focused on our personal quirks and on detriments to other traits we discussed, but there are more.
The first and most obvious one would be your continuing to do the thing you needed to repent for. After all, how could you have true remorse for having done something you still do! But as Ibn Pakudah quotes him, a sage once remarked pointedly that while “no sin is small if you persist in it”, nonetheless “no sin is great if you ask forgiveness for it” and no longer succumb to it.
The other thing about continuing on with the sin in question is that it starts to become all right and out-and-out justifiable in your eyes after a while, until it becomes just “something you happen to do”. But that’s even more nettlesome and alarming, since the one sin begins to gather steam and to sink lower until it becomes a fixed pattern of behavior. Despite that, though, if you reverently ask G-d to forgive you and you break the pattern, it will indeed be undone and you will have achieved teshuva.
You’d also have trouble doing teshuva (again) if you’d relapsed and succumbed to an old temptation after having already gone through all the steps of teshuva. (You’d of course be able to start all over again, but it would be that much harder.)
It would also be hard to do teshuva if you kept putting it off and assuring yourself that you’ll get to it someday, or perhaps after you’d have done everything untoward you wanted to and “gotten it all out of your system”, as we’d put it. But that simply wouldn’t do, for we’re taught that “Anyone who says, `I will sin then repent’ will be denied the chance to repent” (Yoma 88b). And besides, the sad, fearsome truth be known, no one knows when he’ll die, so you might never get the opportunity.
And a sure impairment to true and full teshuva would be your repenting for just *some* of your sins while persisting in others. For while teshuva by degrees is still teshuva and G-d denies no one His efforts, the individual in pursuit of spiritual excellence would settle for nothing less than true reconciliation with G-d after having neglected Him.