Libellus IV

Here is what H.C. Chery, O.P., has to say on the matter of "What sins to confess" in his book, Frequent Confession (the items in bold are a point which I find particularly pertinent):

"A choice is necessary
In church, bu the confessional, I begin my examination of conscience. Of what sins shall I accuse myself?
The question is obviously relevant. For I could not possibly aspire to confessing all my sins. Scripture says that the just man sins seven times a day, and I, who am not a just man, sin in all sorts of ways every day. A complete confession, with an as accurate a total of my sins as possible, is an unattainable dream--and useless as well. A choice must be made. What must I choose?
[We all know mortal sins must be confessed, so I'll skip this part.]

In case of doubt
For some the difficulty is to know when a certain sin is mortal. In theory everyone knows: grave matter, full consent, and full knowledge. In practice, the question often arises, was the matter really grace? And still more commonly, did I really consent? The answer to the first question can easily be found by asking the confessor. As regards the second, by the very fact that I ask myself the question in good faith, sincerly, by the very fact that I am not sure, it is answered; there was not full consent. Does that mean that this 'doubtful' sin, or rahter this 'doubtfully committed' sin, should not be confessed? Not at all. The existence of such a doubt may legitimately allow reception of the sacrament of the Eucharist; strictly speaking there is no obligation to confess such a sin, but it would be wrong to shelter behind this absensce of obligation in order to retain posession of such a doubtful conscience....
[I have skipped also a couple paragraphs on the formation of conscience.]

Venial sins
But I desire particularly to insist here on the examination and confession of venial sins. Isn't it precisely in this respect that those who regularly confess are most deficient? What is the complaint most often on the lips of those who confess frequently? 'Confession is a bore because I always have the same thing to say.' Or else this remark which refers to the confessor: 'He says nothing to me,' meaning nothing out of the ordinary which would force me to bestir myself.
Now these two defects which make confession psychologically tedious are due to the same cause: you do not know how to confess. How do most penitents confess?

Acts not stated to be confessed
Some (a few it is true), forget that sin is an act, not a state, and they manifest (or think they manifest) the condition of their soul by saying: 'I am a liar, I am impatient,' etc. This way of confessing is not the right one. You show thus the inclinations of your soul; but confession is not an account of your inclinations; it is the statement of precise actions, the consequence no doubt of your propensities, but differing from them as the fruit does from the tree. An individual may well have a propensity to lying (being a liar) without in fact having committed sins of lying during the fortnight following the last confession. If such sins have been committed the accusation should be 'I have lied, I have failed in charity, I have been lazy, I have been vain'. This formula is more correct, but as an accusation it is scarcely better, that is, is scarcely more profitable to your soul, scarcely more likely to draw useful advice from your confessor. Why? Because it is colourless. It has not required special thought on your part, nor any attempt at precision. It furnished the confessor with no special distinguishing signs enabling him to see in what way your soul differs from the one that he had to judge and advise before yours. Of the ten penitents who follow you, nine at least may well present the same list--and unfortunately in fact do so. Why (unless he has other knowledge of you) should you expect your confessor to give you exactly the advice you need, you personally and not another? Your personal case has not been shown to him by this confession; it gives him nothing to go on. He would have to possess wonderful psychological insight to be able to divine from this rapid list of 'standard' sins uttered through a grille in which he cannot even see your face, the words he should say to suit your case and incite you to make the effort that you, personally, ought to undertake yourself. All confessors cannot be expected to be like the Cure d'Ars. Usually he will only give back to you what you yourself have provided him with."

"Ha! Meditate on that," Chery seems to say. And he has a point: How many times have I said myself or overheard my friends say, "All he said to me was to make sure I'm saying my prayers every night and say ten Hail Mary's as a penance!" Sometimes it might be the priest, but in my case, at least 5 out of 6 times, I'm sure this has been my own fault. And what advice does Fr. Chery give to help us confess better? You'll have to come back at a later date to find out.