More on cycles - hope this isn't too off-topic. I've been think about this for the last week - ever since the question was asked - why don't we just do it ALL the time. So here I go. Note, these are my own poorly chosen words, so don't be too critical
Paul often describes Christianity as a race. Christians as athletes. We are trying to run a marathon called life. Not just life, but a christian life - satan makes it more like a steeplechase, with pits all around - so it's very difficult to even finish. The finish line, is of course supplied by grace and I by no means intend to say that we can save ourselves, but the struggles described by Paul are clear. So how do we struggle, how do we train to jump the pits as we run, how do we build our spiritual stamina and strength?
As an endurance athlete, I will tell you that it's impossible to train hard all the time. In order to achieve the highest level of stamina and strength it is necessary to train in cycles. First, an athlete must prepare to train - fundamentals, low intensity stuff - if you jump right into the hard stuff, you risk injury and without a good base you cannot build to a new level. So, preparation is just as important as the hard stuff. Next, a period of intense training. This is the hard stuff. This breaks the body down - stresses it farther than it's used to. This can't be done for too long, otherwise you fall into the trap of "over training" and this can take months to recover from. Last is a period of recovery - after all that hard work, you must let your body recover and achieve a new higher level of performance.
Now - the church fathers seemed to have known all these "modern" training techniques 2000 years ago, because they setup the liturgical cycles in a similar fashion - to help the "christian athlete" to achieve a higher level of spirituality (and by this I mean closer to God). Each year we go through a similar cycle of preparation, ascetical struggler and then recovery. (actually it's done 4 times a year, but I'm focusing mainly on the great 40 day fast, aka Lent). Before Lent there is a 4 week preparation period - very important - the fundamental are taught - humilty, repentance, forgiveness - without these, the hard stuff would be meaningless or even damaging. Then Lent - the hard stuff - ascetical fasting, prayer, tithing etc - we intend to overreach our comfort zone in the hope of drawing closer to God. Finally, recovery - no fasting is allowed the week after Easter. We celebrate and renew ourselves, and with God's grace bear His good fruit.
So, there you go - my take on why the church has liturgical cycles. Thanks for reading...