The following comes from the Catholic Exchange:
Sometimes you might fall into some sin or negligence in word or deed, such as disturbing yourself at anything which happens to you, or murmuring, or listening to murmuring, or falling into some dispute, irritation, curiosity, or suspicion of others, or into any other fault, whether it be one or many falls.
In such cases, you ought not to be disturbed or disheartened or saddened at the thought of what has happened, nor be confounded within yourself, at one time, believing that you will never be free from such infirmities, at another, that your faults and irresolution are the cause of them, or again, imagining that you are not walking in the spirit and way of the Lord, with a thousand other fears, pressing down your soul at every step with discontent and cowardice.
Otherwise you would feel ashamed to present yourself before God, or you would do so in a spirit of distrust, as though you had not preserved that faith in Him which is His due. And as a remedy, you would waste time in pondering over these things, scrutinizing how much you harbored the thought and whether you consented to it, whether it was voluntary or was at once put away. And, from taking the wrong road, the more you think of it, the less you are able to make up your mind about it, and the more your weariness, perplexity, and anxiety to confess it increase.
And so you go to Confession with a tedious fear, and, after having lost much time in making your confession, your spirit is even more uneasy than it was before it, for fear that you have not told all. Thus your life is one spent in bitterness and anxiety, with little fruit, and with the loss in a great measure of its reward.
All this comes from not knowing your own natural weakness and the way the soul should bear itself toward God. For after having fallen into all the faults we have enumerated, or into any others, we may more easily approach God by a humble and loving conversion, than by the spirit of grief and discontent at the fault itself, in the case of the examination of venial and ordinary sins, to which alone I now allude. For it is only into such sins as these that a soul that lives in the manner I am now supposing is wont to fall. And I am speaking only of those persons who lead a spiritual life and are striving to advance in it, and are free from mortal sin. For those who live carelessly and in mortal sin, and are always more or less offending God, have need of a different kind of exhortation; and this medicine is not for them. Such persons should be troubled and ought to weep and to make their examination and confession with much thought, lest, through their own fault and indifference, they render the remedy that is necessary for their salvation unavailing.
To return, then, to speak of the quiet and peace in which the servant of God should ever abide, I will go further and say that this conversion must be understood to apply — in order that there might be entire trust in God — not only to slight and daily faults, but also to such as are greater and more grave than usual, if at any time the Lord should permit you to fall into such; even though they may be many together, and are not merely the effects of weakness and frailty, but of willfulness. For the contrition that only disturbed the soul and filled it with scruples will never lead it to perfection, unless it is combined with this loving confidence in the goodness and mercy of God.
And this is especially necessary in the case of persons who not only seek to rise out of their miseries, but would also acquire a high degree of sanctity and a great love for and union with God.
Many spiritual persons, from not wishing to understand this aright, ever bear about with them a heart and a spirit broken and distrustful, which hinders their spiritual progress and capacity for the higher graces, which one after another God has prepared for them. These often lead a sort of life that is very wretched, useless, and pitiable, because they will follow only their own imaginations and will not embrace the true and wholesome doctrine that leads by the royal road to the high and solid virtues of the Christian life and to that peace which was left us by Christ Himself.
Such persons, whenever they find themselves in some disquietude through doubts of conscience, should seek the counsel of their spiritual father or of someone whom they think capable of giving them the advice they need, and should commit themselves to him and rest entirely in his judgment.