You probably won't be expecting it, but it is likely to hit you as soon as you get here--when you get rejected from your first freshman seminar or strike out at the opening mixer. Harvard is a competitive place: the full resources of the University are by no means open to all its students, or even apportioned democratically a long them.
For a lot of Harvard students, the competition here is the rudest of all freshman year shocks. You won't hear about it through any of the official channels before you arrive here--they'll all tell you how open and full of options Harvard is. That's partly true, of course, but about 300 of you will still not be allowed this spring to enter the field of concentration that interests you most. All of you, without a doubt, will emerge from your freshman year wearing the scars of some sort of competition.
By the end of freshman week, it's already in full swing. Besides the seminars--tremendously appealing small classes that accept far less than all their applicants---and the mixer, there will be conversations in the Union in which people compare SAT scores and introductory meetings for pre-meds and pre-laws.
Things die down for a few weeks, but then perhaps you'll get the urge to join some undergradutae organization and find you have to go through an elaborate selection procedure in order to work on anything from the Bach Society to The Crimson. Things come to a peak in the spring, when you have to choose a concentration. There are about five of them with interdisciplinary programs and loads of individual attention of students, and you have to survive applications and interviews to be admitted. Then there's House selection. Some of the upperclass Houses are naturally more popular than others so somebody always gets screwed.
By the end of the year, you'll breathe a sigh of relief, being safely ensconced in a House, a field of concentration, a circle of friends and set of things to do in your spare time--but it's by no means over yet.
Things subside a bit for a couple of years but the competition is still very much there, in subtler and infinitely more complex forms. It becomes a way of approaching Harvard life in general, and an end in itself instead of a means for getting what you want here. You'll compete in the dining hall, in class, in bars. It will become second nature to you, so that bu the time senior year rolls around the wave of application for graduate schools and fellowships that you'll spend much of your time filling out will seem like an appropriate finish to your Harvard career.
There's not much need for a lot of the competition that pervades Harvard life, but it's easy to see why it goes on and why students accept it. When people come here, they've probably already fallen into the habit of drawing their self-esteem through their achievements and not anything more abstract. So at Harvard, an achievement-oriented place, people stay within their old patterns of self-identification. Harvard is the kind of place where you can feel more like a person if you're in Social Studies, say, than if you're not.
There are any number of ways to deal with it all. You can immerse yourself in the competition, becoming an expert at snowing interviewers and soliciting recommendations. Or you can forget about it all, and have a college career low in prestige but full of peace of mind.
But don't let the competition at Harvard turn your head and dominate your career here. If you ignore it it won't go away, but if you don't take it all very seriously you'll have a good chance of emerging from four years here psychologically intact.