The Passion narrative begins in Mark 14, with a description of a Passover meal between Jesus and his disciples. This meal and the Passover holiday in general are characteristic and essential to Jewish religious identity, and all of the nuances of the particular significance of that meal are not as valuable in terms of application as they are in terms of interpretation. Jesus and his disciples were Jews, doing what Jews did. Jesus as depicted in the gospel stories was not instituting a new religion, but was attempting to interpret a stale tradition that was failing to provide the societal benefits that it had the potential to offer. Thus, the Passover meal takes on new connotation for the early Christian church. This story is described similarly in the gospels of Matthew and Luke, and the gospel of John portrays an extended version of the evening with some lengthy speeches by Jesus. Paul also describes the Eucharistic rite that evolved from this tradition, in what is probably the earliest recorded indication of the ceremony practiced by the early church.
Some have looked at the Jesus mythology as a vessel for astrological symbolism, theorizing that the twelve disciples represent the full zodiac, and so on. In such a theoretical reading, the water bearer in Mark 14:13 is seen as Aquarius, the age that would follow the age of Pisces, which Jesus could be seen to usher in. The rampant symbolism of fish (the symbol of Pisces) and fishermen in the Jesus narrative is used as evidence of this interpretation, although the value of such an understanding is unclear aside from removing the story from the realm of historical validity. Astrological ages are about 2160 years, so no one alive in Jesus' time or even today will experience crossing the threshold into the "Age of Aquarius," but it is curious that the Gregorian calendar shifts to year 1 of the Current Era right around the time when the sun moved from Aries into Pisces. Not that there is anything applicable to day-to-day life in any of that.
Scholarly research into the practices of Judaism in the first century also inform some readings of the Passion story and the so-called "last supper." That there was a common practice does not lend any validity to a fictionalized account of the practice, although there are some who believe that proof of historical validity is more important than personal application. Some of the story, such as the identification of Judas and the pronouncement of woe upon him, is obviously commentary that developed in early church tradition. Likewise, the prediction of Peter's denial has the quality of folklore, particularly since it could only have been related by Peter, and Peter isn't telling the story. As the first "pope," or head of the Christian cult, a lot of mythology rose about Peter, some of which exalts him and some of which criticizes him; both types of Peter stories are found in the gospel narratives.
What does one do with such a tale, then, aside from read it as the mythology of another culture with an exclusive purpose to relate the story of their god-man figure? One might interpret the universal value of ritual in the lives of human beings. One might recognize the value of community. Some people develop doctrinal statements from this account, but there honestly isn't enough here to warrant any doctrines. The Jesus of the gospel of Mark doesn't even mention "the forgiveness of sins," as some of the later narratives amend; to read this narrative is to glimpse a theology and mythology of early Christianity that is still developing. It is interesting that the quote from Zechariah about striking the shepherd and scattering the sheep was originally in the context of striking down religious leaders that promoted idolatry, thus equating Jesus with a bad priest and his followers as idolaters. Perhaps the authors of Mark were clumsily attempting to frame the quote in a new context.
Honestly, I don't know what you do with the story, aside from call it a story and move on. We all do things out of fear, like the character of Judas. We all promise things we really shouldn't promise, like the character of Peter. Many of us wind up listening to those well-intentioned promises, knowing they aren't trustworthy, like the character of Jesus. Even though we can relate to various characters in a story, we run into trouble when we attempt to extrapolate precise behaviors from mythology, because we will never be in the precise positions of anyone in the narrative. Instead, the importance may simply be in recognizing the nature of community, something we all need and for which we all search, but rarely devote the necessary time and energy to fully develop.
This band of people represented in the story of the "last supper" are a community in the process of becoming. Only the visionary leader understands the value of deep community with any fullness, and he is about to disappear. He has prepared the people around him through his examples for a period of time, demonstrating that character and values are more important than rules and appearances. The Passion story in Mark begins to narrate the end of that biography, but this is only an introduction to the life of a community. Community is hard work, and it requires sacrificing some things that have become comfortable. Ultimately, that is what this story is about. Not the Jesus character, but the community that was inspired by him.
That doesn't have to be your community; there may some really good reasons for it not to be your community. Yet we all need some kind of community, and meaningful, deep connection with other people always requires a bit of investment from us. We will make promises we can't keep, we will sit dumbfounded while other people take action, we will experience disillusionment, and we will participate in disagreements. We will have the opportunity to extend forgiveness, take action, inspire, and be peace makers. The values we hold will always be more important than the rules we follow, and the inward character we cultivate will always be more valuable than the outward appearances we invent. Our lives are interdependent, and we are worth one another's deep commitment to community.