That's where the pastoral care you are to be receiving from your priest should come in. While I didn't talk about it previously, since you asked about the length and severity of the fasts and not about exceptions or ways to fast, Shane is right that there are situations that will lead people in the same church to fast differently. The Church is not unreasonable or overly rigid in its application of fasting rules. What I have mentioned are the norms as I understand them, but there have been times in my own life when I have been specifically told
not to fast, for various reasons. This is not to say that if you go to your priest and say "It's hard, so I'm not doing it", he'll automatically say "Oh, okay; stop fasting, then", but that ideally there should be an open and honest enough relationship between a priest and his spiritual children that you can go to him when you are having those kinds of troubles, and he can advise you in a way that is tailored to your situation as he understands it. Being the only Orthodox Christian in my family, for instance, always presents challenges for me when I go home to visit around the holidays, not only because I inevitably miss the last bit of the Nativity fast (as well as the Nativity feast), but because obviously nobody around me at home is fasting. In that case, my priest has assured me that I can modify the regime as appropriate so as to not make a show of my fasting -- i.e., if we eat a home-cooked meal, I eat whatever is served to me and am thankful for it, but if we go out to eat and there is a vegetarian option, I should order that without mentioning why, since it's nobody's business but God's how I am fasting. There is in fact a story in the Sayings of the Desert Fathers (forgive me, I cannot remember off the top of my head which father/s it concerns) of a pair of monks who are friends and reuniting after a long period of not seeing one another. In celebration, one brings a bird for them to eat. This prompts the father to say "I'm sorry, but since I have become a monk, I have not let meat into my body" (I can't eat that). His friend replies "I understand; since I have become a monk, I have not let anger reach as far as my throat." This moves the first monk to apologize and ask for forgiveness, since he recognizes that his friend's way of fasting is the true and best way, even if it includes meat which monks normally do not consume.
With all that said, I would feel confident that as a new member of the church, no priest would put you through a rigorous fasting regime. My first fast after I was baptized was very difficult for me (and I don't remember for sure, but I think it was Jonah's, the three-day fast...hahaha), even though I had been trying to ready myself for it by participating in the the Wednesday and Friday fasts of my own volition. I even called up a friend of mine from church and explained to him that I was feeling light-headed and unwell, and he (just a regular layman, like me) immediately told me to stop fasting and go eat something. The fast is not meant to be an endurance test and it is certainly not meant to endanger your health or your life. We keep these fasts because they are handed down to us by our fathers as means of spiritual discipline, not for their own sake. So if you have trouble with abstaining from dairy, for instance, but your prayers on this account and in other areas are tripled during the fasts, you are still progressing. If you abstain from hateful words, you are still progressing. Spiritual fitness is the goal. As is often said, we don't look at a brother's plate. (Read: Judging someone's fast is worse than not fasting at all.)
Orthodoxy is interesting in this regard for someone coming from an RC background as I know both you and I do, since outwardly it seems very harsh and extreme (relative to Western Christianity, which does not fast at all in the modern day), but inwardly it is very merciful, pastoral, and pragmatic. I thought to myself, prior to converting, that I could never make it through 55 days of Lent that included actual fasting, rather than the Western-style view of "What individual habit am I going to sort of try to not indulge in so much?". Lo and behold, at the end of my first Lent I was actually chastised (lightly, since everybody knows I'm new and liable to make mistakes) by the priest for not
stopping fasting for the Holy Fifties! I had gotten so used to the rhythm of life during the fast, that I completely ignored/forgot that there is NO fasting for the 50 days after Easter. I don't know why, but I guess I thought that we must still keep the Wednesday and Friday fast, so when I asked Fr. Philemon how I could handle having out-of-town visitors that Wednesday and Friday, he was confused. "What do you mean?" "You know, for the weekly fast?" "What weekly fast?" "The Wednesday and Friday fast this Wednesday and Friday?" "WHAAAT? You are still fasting?! Oh no, no, no! You know that there is NO fasting during the 50 days after Easter, right? This is the time to enjoy the new life with Christ!" One of deacons, after having a good chuckle, told me he sometimes forgets too, but I think he was just trying to make me feel less embarrassed. Haha. With the kind of schedule our church keeps, it is just easier to assume that we are always in a fasting period, but that is not always the case.
