Something puzzles me a bit concerning the Eastern theology. Perhaps you could help a western Catholic to understand it. In RC, if you violate the fast or abstinence, it is a sin, either mortal or venial, depending. And there are times when the bishop has declared the fasting to be voluntary, so in those cases, it would not be a sin. However, in the Eastern Churches, am I right to say that it would not be a sin if you violate the Lenten fast, but at the same time, you are expected to try your best to obey it. The Eastern Lenten fast is pretty severe.
In western Catholic theology, if you die with one mortal sin on your soul, then you go to hell. If you die with lesser sins, or if some of the larger sins have been forgiven, but there still might remain some stain, due to the fact that your repentance was imperfect, then in that case, you go to Purgatory and are purified there, but in that case, eventually, you will go to heaven. So, basically, for a western Catholic, you are safe as long as you do not have an unrepented mortal sin on your soul when you die.
Now how would that work for an Eastern Orthodox. For example, there are no mortal or venial sins in the Orthodox Church, is that correct? And at the same time, you do believe in hell? So how then will it be determined who will be saved and who will not. What does an Eastern Orthodox have to do, in order to attain eternal salvation? For example, if he does not try to keep the Lenten fast at all, and he attends the Liturgy, once a month. Will that person be OK ?
I don't want to oversimplify my answer, I must be brief but I can't just let a thought hand out there. I am also not the best person to address this, being relatively new to Holy Orthodoxy myself.
The concept of sin is very real in Orthodoxy, make no mistake about that. But in my understanding (subject to correction here) there is no hard and fast distinction between categories of sins. 'Mortal' and Venial' seeming to be like buckets we can toss examples of each sin into, Orthodoxy doesn't really think much about these buckets.
We might focus on the tendency to sin more so than each event (or incident), trends maybe. And it is helpful to understand the basic idea of salvation by Theosis (Divinization), becoming Godlike (in the sense of growth by imitation or emulation). It is a very old concept but not well received in the west anymore.
We can look at Theosis as ongoing development with each phase of our lives and church cycle as growth experiences, ascetic practices as real "exercises". If the doctor (one's Spiritual Director) prescribes a certain regimen, and we follow it, hopefully we shall see some improvement in the patient (the Christian). Strength, stamina, alertness and a positive outlook might be the benefit. Ascetic practices should strengthen one's resolve, help the spirit master the body, make it possible to resist sin. These are all positive benefits.
Neglecting these will mean the Christian will not reap the benefits, there will be lack of progress. That in a way is it's own punishment.
If we make these "penances" to be a lot more like arbitrary rules to follow, with unrelentingly stiff penalties attached (like damnation?) they can very well be counterproductive, and people may perform them for the wrong reasons or only for a while, perhaps not out of love for God but out of fear. Faced with such a high bar and negative reinforcement, some people (especially new Christians, and the young) elect to "opt out", the religion loses credibility with them.
I don't know anywhere else in human society where such an approach works well with people. "If you don't do your piano lessons I will burn your fingers!" rarely forms great pianists, "If you don't do your exercises, I will beat you to a pulp!" will not make good gymnasts. Why should "if you don't complete your fast, I will burn you in hell!" work any better?
The desire for success at these endeavors should rise from inside the person, they should love the music and wish to make great music, love the sport and want to break records, love God and seek Him. People can and will endure many trials to achieve those lofty goals, positively.
We have all read "Watch and pray, that ye enter not into temptation: the spirit indeed is willing, but the flesh is weak." and understand just what that can mean to us. The purpose of ascetic practice is to train the will and tame the flesh. That is a real growth prospect for us, to put on Christ. It is a very positive thing.
But one needs to be a real Christian first, these things will not make us Christians. Attempting to follow the "rules" of penance under threat of damnation can be dangerous to weak faith, it is a poor foundation for growth. That is why I recall St Paul stating "I want to learn only this from you: did you receive the Spirit from works of the law, or from faith in what you heard?" The monks of the desert did not arise in a vacuum, they came out of Christian communities elsewhere and determined to work hard for their salvation. Not everyone can do that, not everyone is at the same level.
Once we believe, and desire Him, we will bear the burdens, we will take up our crosses to gain Him for ourselves, we embrace the rules (the "Law" if you will). Until we have reached that point a little understanding is in order. I think that is probably why the church has this high bar set before us, and all of that patience and compassion for us along with it.Michael