The world that you normally experience as reality -- which is really a construct, one that has been made up by you, your parents and teachers and the other influential people in your life, plus all of your particular experiences -- will be called into question during this time, and depending on certain factors, you could be drawn as a result to someone who is emotionally unstable and generally irrational. This period will especially affect you if you don't have much of a sense of your own spirituality. Everyone has a spiritual soul, after all, but not all of us discover it, at least not until later in life.
If you're a late bloomer in that regard, you could meet someone during this period who really turns you on to the more mystical side of life. They'll seem incredibly tuned in to a kind of spiritual awareness that you'll very much want to tap into yourself. But since this is someone else's spiritual reality and not really your own, you could really be led astray, buying into all kinds of ideas and spiritual practices that not only aren't you, they won't work for you and your life. A spiritual awakening is possible, but make sure it's on your own terms.