Our gemara on Amud Beis mentions a concept of Tzarich, V’eyn Lo Takana.  That is sometimes a Mishna or Beraisa may note that a certain action is required, yet there is no way that it can be made up.  The obligation stands with no ability to fulfill it.

There are times in life where we must face the consequences of deeds that cannot be undone.  

It is understandable that a person can feel crushed because of what he or she has done.  It could very be that there is indeed no way to fix the physical damage of what happened. 

In the realm of repentance, we are taught that we can always be forgiven. There is nothing that stands in the face of repentance (Rambam Laws of Teshuva, chapter 3:14). Yismach Moshe on Ha’azinu (1:14) makes this point clear.  Despite it stating in Koheles (1:15) that there are physical effects of sin that cannot be undone, such as the birth of an illegitimate child, the sin can always be undone.  He goes on to say, even if a Heavenly voice were to call out that he will NOT be forgiven, he is no way limited by this, and still can be forgiven.

While you might be thinking, “Yeah, but the damage is done.  The divorce happened. The car accident happened.  This can never be fixed.”  This is true, and not to be callous about the suffering caused, the world is filled with awful things that happen. Yet, we say it’s God's will.

You will argue, “It’s one thing natural disasters.  BUT - I - CAUSED - THIS --- NOT - GOD!

To this, you might find comfort in a radical idea mentioned in Tzidkas Hatzaddik (40 and 43). His position is that although one must make every effort to resist sin, and even at the time of what feels to be a temptation that cannot be overcome, one must struggle valiantly to resist. Nevertheless, ex-post facto, it is quite possible that one was facing an urge that was beyond the ability to manage.
While one can never use this as an excuse to duck out of resisting sin, since one must always try his best, Tzidkas Hatzaddik posits that indeed it is possible to be presented with a compulsion to sin that cannot be managed, and effectively be considered an oness (a person under force and not liable). He goes further to deduce that in those cases, since the person cannot resist, it must effectively have been God's will, and then for all intents and purposes, a mitzvah! According to this almost reductio ad absurdium tautological analysis, in hindsight, the only thing that was actually sinful was that the person's intent was for self-gratification instead of carrying out G-d's will.  Therefore, Rav Tzaddok suggests, when one does full and sincere penitence, he restores this final step and aligns himself with God's will, turning all his acts into mitzvos. This is how he explains the rabbinic dictum Clearly, this is a radical position and can easily lead to rationalizing sin and also make morality seem precariously relative, however it also is comforting and redeeming.