The Mitzva to wear Tzitzit on a four cornered garment, is designed to be the object of remembrance. When we see or are aware of the Tzitzit in our bodies, we are to remember all of the commandments of the Torah.
The Sefer Hachinuch gives a rationale as to the importance of returning a lost article. He writes that שכחה נמצאת אצל בני אדם, that forgetfulness is a very common trait. Therefore, when a lost article is returned, it brings that person great joy. Rabbi Avraham Twerski was constantly urging his students and readers to study book of Mussar, discipline. Not only do these books help keep us focused as to what is truly important in this world, they also help us remember.
It is a terrible feeling for a person to feel taken for granted. Sometimes because that person is always there, and easy to rely on, it is also easy to forget to acknowledge his kindness. The Messillat Yesharim points out that there are many basic beliefs in Judaism, that we are aware of, but we tend to fail to give these beliefs the priorities that we should. For example, if you ask any believing Jew, if love of G-d, or fear of G-d is important, they will answer that, of course, they are important. But if you ask when was the last time you did a self check as to how you are doing in your love and fear of Hashem, you are likely not to have remembered.
This is why the wearing of Tzitzit is essential in strengthening our observance of Mitzvot. We desperately need to remember what is important in life, and what is not.