Well, think of it this way,
we are told to love others as ourselves, and so if it’s prideful to hold a grudge against someone else, then it must likewise be prideful to hold a grudge against ourselves as well,
we know pride is the root of evil, but to explain it more simply, pride is an inordinate esteem of oneself, it’s considering yourself better than you really are, or in this case it’s thinking “i should have done better, i am so disappointed in myself!” when in reality, that is just what you are capable of(sin), and it’s only by the grace of God that you could do better, and not by yourself.
pride is the vice of deception, just as we call the devil the “father of all lies”, he influences us to think these things of ourselves that are not true, leading us into hidden prides which we take as humility,
but humility is the virtue of truth, it keeps us from reaching beyond ourselves, and it leads to an orderly love of yourself with respect to God and your neighbor,
although to make it easier to discern between vice and virtue, look at it this way - vice is inordinate, and virtue is orderly, and so if something is out of place or out of order in your spiritual life, then you know there is vice present,
a good way to know is simply to ask yourself, do i have peace or not?
we should be able to have peace, as i said earlier, even amidst our sins, although not with a willingness to commit them, but just with the willingness to get back up and try again,
and that book “searching for and maintaining peace” will explain all of that in greater detail, all the whys, whats, and hows, and that other book i linked to will also address those things, but it also addresses every other aspect of the spiritual life, whereas the other book addresses specifically on peace of heart.
and to know whether or not you are acting by certain vices rather than virtues, you also just need to learn your religion better, such as reading from the writings of the saints, like saint Alphonsus de Liguori, or Saint Francis de Sales, or the Cure of Ars…or really anything on
www.tanbooks.com
and then it also just takes a serious and honest examination of conscience each night, and alot of prayer, especially during Holy Communion, for guidance and the grace to see yourself as you really are.
well, if you have any other questions, i’d be glad to help further,
ok, take care.