The unreliable narrator is a potent but tricky device in fiction. To use it effectively, you have to stay outside the character, and be aware of his self-delusion, but at the same time you have to have a real empathy for the character's thought processes.
Tolstoy nails it with this characterization of feckless lover Vronsky. As the passage starts, you can almost believe, with Vronsky, that he's acting responsibly. But that illusion is stripped away, one detail at a time, even as Vronsky goes on believing it.
Watch how Tolstoy slips out of Vronaky's mind just once, to reflect on how others share Vronsky's complicated financial state -- and how even that is a trick. Tolstoy's omniscient narrator is as unreliable as Vronsky.
In spite of Vronsky's apparently frivolous life in society, he was a man who hated irregularity ...In order to keep his affairs in some sort of order, he used about five times a year (more or less frequently, according to circumstances) to shut himself up alone and put all his affairs into definite shape...
On waking up the day after the races, Vronsky put on a white linen coat, and without shaving or taking his bath, he distributed about the table moneys, bills, and letters, and set to work...
Every man who knows to the minutest details all the complexity of the conditions surrounding him, cannot help imagining that the complexity of these conditions, and the difficulty of making them clear, is something exceptional and personal, peculiar to himself, and never supposes that others are surrounded by just as complicated an array of personal affairs as he is. So indeed it seemed to Vronsky. And not without inward pride, and not without reason, he thought that any other man would long ago have been in difficulties, would have been forced to some dishonorable course, if he had found himself in such a difficult position. But Vronsky felt that now especially it was essential for him to clear up and define his position if he were to avoid getting into difficulties.
What Vronsky attacked first as being the easiest was his pecuniary position. Writing out on note paper in his minute hand all that he owed, he added up the amount and found that his debts amounted to seventeen thousand and some odd hundreds, which he left out for the sake of clearness. Reckoning up his money and his bank book, he found that he had left one thousand eight hundred roubles, and nothing coming in before the New Year. Reckoning over again his list of debts, Vronsky copied it, dividing it into three classes. In the first class he put the debts which he would have to pay at once, or for which he must in any case have the money ready so that on demand for payment there could not be a moment's delay in paying. Such debts amounted to about four thousand: one thousand five hundred for a horse, and two thousand five hundred as surety for a young comrade, Venovsky, who had lost that sum to a cardsharper in Vronsky's presence.
Vronsky had wanted to pay the money at the time (he had that amount then), but Venovsky and Yashvin had insisted that they would pay and not Vronsky, who had not played. That was so far well, but Vronsky knew that in this dirty business, though his only share in it was undertaking by word of mouth to be surety for Venovsky, it was absolutely necessary for him to have the two thousand five hundred roubles so as to be able to fling it at the swindler, and have no more words with him. And so for this first and most important division he must have four thousand roubles. The second class--eight thousand roubles--consisted of less important debts. These were principally accounts owing in connection with his race horses, to the purveyor of oats and hay, the English saddler, and so on. He would have to pay some two thousand roubles on these debts too, in order to be quite free from anxiety.
The last class of debts--to shops, to hotels, to his tailor--were such as need not be considered. So that he needed at least six thousand roubles for current expenses, and he only had one thousand eight hundred.