The Tanya in chapter 18 (and chapter 2 alludes to this as well), says the following:
"At times, the sinners of Israel may even bring down (for their children) very lofty souls which have been in the depths of the klipos, as is explained in Sefer Gilgulim)".
I will quote a paragraph from the English "Lessons in Tanya":
"A lofty soul that has fallen captive in the hands of the kelipot, is sometimes released by the Kliipot willingly. Anything in the hold of the kelipot cannot be wrested from them against their will, for the principle that "God does not make unjustifiable demands of His Creations" holds true even with regard to the kelipot. In the case of a child born to sinful parents (here I would add that in some cases it may not be sinful parents. It may be simple decent parents that simply weren't learned or educated in spiritual matters), the kelipot willingly release the soul, in the hopes that such children will be influenced by their parents, and will become sinners like them (or in the case of simple parents, the kelipot assume that the child will just follow the simple way of life of his parents and not transcend beyond that point, i.e. nothing great will come of him anyway). In this way, the kelipot stand to extract an even greater measure of vitality from the holiness of the soul by means of its eventual sins.
HOWEVER, HAVING SUCH A LOFTY SOUL, THE CHILD HAS THE ABILITY TO OVERCOME THE OBSTACLES IMPOSED ON IT BY IT'S PARENTS WICKEDNESS (or transcend the parent's less lofty state of soul), AND MAY RISE TO THE LEVEL OF THE TZADDIK.
In this way, paradoxically, it comes to pass that a tzaddik may be born to wicked parents BECAUSE of their wickedness (or, a Tzaddik may be born to simple parents BECAUSE of their simpleness)."
My friends, despite past failures, even of many years, who told you that you do not have this lofty and special soul?
The fact that you only see ugliness means nothing at all. That is the Yetzer Harah's biggest cover-up. He hides that lofty soul from you.
But you need to start looking.
And you will find this spark.
But even after you do, he will tell you that it is not worth fighting for because all you are doing is unscrewing a screwup, you're just a low janitor that cleans vomit off the floors and walls. And at the end of it all, you may have a clean house but a very empty one. Look at that Tzaddik there who was learning Torah and doing mitzvos for 90 years. Now THAT'S A HOUSE!! You? You have nothing at all.
Drown out that voice because it is false. Hashem knows that many of us were put into environments and situations that are not attuned to Kedushah and we have to fight 10 times harder than that other Yid who has Shas in his head, the one who knew all those Rav Akiva Eigers when he was still in pampers, the one who quotes the Shav Shematza in a muffled voice because he is still sucking on the pacifier, the one who finished all of the Mishnayos on his 8th birthday, and the one who, for 50 years, does not know what his wife looks like, who finds relations distasteful, even with his good and beautiful wife, because he gets a greater joy from figuring out pshat in the Rashba, the ones who never - or rarely had - those dark nisyonos that we do.
Hashem tells you:
"You are wondering to yourself why is so hard to stay a good and clean Jew even for a day, even for an hour?
Stop wondering, and stop trying to second guess Me.
Because that is why I created you, and that is what gives Me the most nachas, that actually causes the Heavens to shine and all the malachim to sing.
And that is why you are the ones that will bring the Third Beis Hamikdosh down from the Heavens onto the Har Habayis.
Because I wanted that all along: That nail-biting, gut-wrenching, blood-stained "10 or 100 times harder" fight that you fight for Me, every hour of the day.
That is why I love you so much."