I want to clarify what the question is, deal with a commonly wrong way to answer this question, and in exchange, suggest a possible answer. Please feel free to chip in with your own answer: More than anything, I am exploring the question in this post, not offering a definitive and exclusive response to it.
Here's what I mean by 'making sense' of short-term assignments. Although it's common knowledge that people need some kind of meaning for their lives, this need seems both more intense and harder to satisfy for short-term experiences.
Harder to satisfy, because a few brief months does not allow time for visible evidence of meaning to build up. Although career missionaries point to years of service on the field, short-term missionaries have it more difficult. Much as I enjoyed my time, I remember a few students befriended, some 'deeper' spiritual conversations that perhaps involved Dante or some future post-high school plans; twenty weeks of Bible study. That's all. As with any short experience, there is no large buildup of concrete, visible evidence to signify meaning.
More intense, because we who travel or do missions or other short-term assignments are moving on to something else: It's important to know that a few months teaching at a small school was a good choice, that spending a year at an unexciting job achieves more than just keeping the electricity on, that a summer in Spain does more than give us an appreciation for gelato. Lacking clear long-term evidence of meaning, we also lack a sense of purpose in short-term assignments.
A Bad Answer
Ok, so not all bad. But the most common answer is also an incomplete one. Primarily, we American Christians tend to anticipate that the meaning of short-term assignments will be visibly revealed in the weeks and months and years to come after the experience itself ends.
Here are a few possible examples, the way the question is raised and the common but incomplete answer:
Question: Why did I spend six months teaching in Europe?
Answer: Perhaps in the future, I will take students of my own over here and push them to teach in Europe.
Question: Why did you get that humanities major in college, when you're in the military now?
Answer: Probably because you will teach that subject in the future.
Question: Why did you spend a summer studying abroad?
Answer: Maybe you will meet someone from that country, and use the language and culture to share Christ with them.
Whatever the scenario, we believers are continually trying to pinpoint a specific event or situation in which our previous short-term experience bears visible fruit and thus proves itself meaningful.
Perhaps an analogy is a better way to think of this exercise: In many ways, the imagined Christian life is like climbing a mountain. Perhaps we cross a stream. Perhaps we turn left, then in five minutes, right again. All of this turning is quite confusing at the moment. But then we reach the top of the mountain, look down: Lo and behold, the left turn protected us from a rock slide; the right turn advanced us five yards further up the hill. And suddenly it all makes sense.
Like climbing a mountain, we believers expect to 'look down' at the previous weeks and months and years of our lives and have them make sense; we want to articulate how each turning of life actually helps us. Thing is, we never reach the top of the mountain in this life. Ever. And because we are still 'climbing' metaphorically, some of those metaphoric turnings never do make sense to us.
Perhaps the best answer to this problem is to throw out the 'mountain' mentality, to stop hunting for scenarios in which short-term experiences take on new meaning, stop trying to clearly articulate the purpose of certain brief moments in life.
Imagine a quiet stroll through the mountains. At times, the peak is visible; other times it disappears again. Maybe you walk up a hill towards the treetops; five minutes later, you're headed down again towards a stream and a patch of orange flowers. No one stop on the way leads into the other or has any visible purpose, so to speak: In other words, the orange flowers do not make a glimpse of the mountain possible. Had we turned back down the path without seeing the mountain, the flowers would still be just as beautiful.
Like this mountain path, the experiences of life are meaningful as we are in them, experiencing them now. Just as the orange flowers can be enjoyed without seeing the mountain top, so we can enjoy short experiences without knowing what they lead to, what comes next, whether they make any subsequent experience possible.
My own six months here have been immensely enjoyable, profitable for me and (I hope and pray) for those around me. My friends have taken on jobs, done graduate study, done summer trips that never clearly led into anything else, but each of these experiences - job or study or trip - was itself meaningful while they were in it.
It is not in some future happenstance or concrete, visible event that God works. He works in the immediate present in us, and it is that immediate present, detached and invisible from both past and future, that He invests life with meaning.
Eventually, every brief experience and also the great entirely of life itself, will take on a clear and articulate meaning. Paul assures us that "we all, with unveiled face, beholding as in a mirror the glory of the Lord, are being transformed into the same image from glory to glory, just as by the Spirit of the Lord" (II Cor. 3.18). Those words 'being transformed' suggest a continual, never-ending work: In other words, every momentary experience, every day, even every breath we draw takes us believers a step nearer the place where we see and
are seen in Christ's own image.
Until that time, though, it is our responsibility to live in the present and to draw meaning from the present workings of God.
Quick now, here, now, always--A condition of complete simplicity(Costing not less than everything)And all shall be well andAll manner of thing shall be wellWhen the tongues of flame are in-foldedInto the crowned knot of fireAnd the fire and the rose are one.~ T.S. Eliot, 'The Four Quartets'