not sure I get all of your question, but we are not obligated to perform specific penitential acts every day. The nuns used to teach us to “offer it up” in other words to accept the numerous daily pains and disappointments of life in a spirit of cheerful acceptance and willingly endure the physical or psychological hurt with a conscious intention to offer that tiny bit of suffering for the poor souls in purgatory. It was a way of teaching children how to cope with the minor frustrations as well as the deeper pains and sorrows of life in the world, and a very healthy attitude. Far healthier anyhow than the attitude of adults who try to shield children from every frustration and disappointment.
The Church has traditional penitential practices and different ages have viewed personal penance in different ages shaped by the culture of the times. The new Catholic especially should be guided by their confessor or spiritual director before attempting anything beyond the current disciplines. For instance while in my childhood the Lenten fast was every day of Lent except Sundays, now it is only on Ash Wednesday and Good Friday, but a Catholic so motivated could voluntarily keep that as their Lenten discipline.
yes the conscious decision to “offer it up” for the poor souls or for a specific person we have been asked to pray for is necessary, not for God’s benefit but for ours, so we avoid the attitude that we are doing this to gain brownie points or to have a good opinion about our efforts. The very act of making that prayer intention is an expression of love toward that person we are doing it for.
You are quite right the proper spirit for penance is essential and as with all prayer and good works, the intention is to perfect our own sinful inclinations and to conform our own wills more closely to God’s. There are also practical benefits that are acknowledged even by psychology and the secular world, such as behavioral or habit training. But we don’t fast for instance, to lose weight even though that may be a good side effect, but we don’t reject the beneficial result either.
Penance also is immensely helpful in overcoming sinful habits and inclinations and disciplining the will and should always be united with prayer and works of charity. In fact if the penance is leading to uncharity (crabbiness, grumbling, resentment) that is time to re-evaluate with the help of spiritual direction.
That’s a wonderful attitude! There’s no reason not to perform an act of penance on any given day. Granted, there are days in the Church year when our hearts and minds are not turned toward penance but rejoicing (e.g. Easter, Christmas, Pentecost), but there is no rule that says “No penance allowed on these days…”
God already knows, but a big part of prayer is instilling good habits in the person praying. Jesus knows I love Him, so should I not say “I love you, Jesus” anymore? The more you explicitly announce your intentions to God, the more you pray, the easier it will be to have a habit of prayer and a habit of meaningful penance.
Penance is a very wide term. One form of penance is mortification, a form of Christian asceticism, the practice of self-discipline and penance to overcome sinful tendencies and grow in virtue. The word comes from the Latin mortificatio, which means “a killing; a putting to death.” St. Paul wrote of the practice to the Romans: “put to death the deeds of the body” (Rom. 8:13) and “make no provision for the flesh, to gratify its desires.” (Rom. 13:14) To the Corinthians, he wrote: “I pommel my body and subdue it, lest after preaching to others I myself should be disqualified.” (1 Cor. 9:27) And to the Colossians, the same: “Put to death therefore what is earthly in you.” (Col. 3:5)
In St. Paul’s first letter to the Corinthians, he admonished some of them for eating and drinking (and getting drunk!) when they assembled for worship, while others were going hungry. (cf. 1 Cor. 11:20-21) Avoiding normal food before receiving Communion helps to remind us just what it is we are receiving in this sacrament, and to approach the Eucharist with proper reverence. St. Justin Martyr, writing to the Roman Emperor Augustus Caesar in the 2nd century, explained that “not as common bread and common drink do we receive” the Eucharist, but that it is “the flesh and blood of that Jesus who was made flesh.” (Apology I, 66)
Fasting is also a traditional Christian mortification (a discipline of bodily self-denial). Mortifications serve to subject our bodily desires to our spiritual needs. St. Paul wrote to the Corinthians “I pommel my body and subdue it,” because he was aware that his bodily urges could jeopardize his spiritual well-being. (1 Cor. 9:27) Fasting was practiced by numerous figures in the Bible – such as Moses, Elijah, and Jesus – to prepare themselves for what was to come. By putting aside our corporal need for food and drink – especially if we fast for more than just an hour before receiving Communion – we can use our bodies’ natural reaction of hunger to stir up in our souls the spiritual hunger we should have for our spiritual food, the Body and Blood of our Lord. We fast while we wait for Jesus, the bridegroom, and that fast ends when we receive the bridegroom in Holy Communion. (cf. Luke 5:34-35)
(That addresses fasting before Communion, for the most part. But fasting is done at other times, as a form of penance, as a spiritual discipline. I would say that the basic idea of fasting is to remind yourself, through your bodily appetites, that you depend on God for your sustenance and well-being.)