Counting numbers. It can be so boring that people count sheep to help them fall asleep. If counting is such a yawn, why would G-d make counting the Omer a mitzvah (Leviticus 23:15-17)? Traditionally speaking, the Omer was to commemorate the barley harvest (ibid., 25:10-17) by giving the omer offering, during which they counted the Omer. In a calendrical sense, the counting of the Omer and the barley harvest took place at a time that signifies change. The harvest represented a change in agricultural seasons in which one enjoyed the fruits of one's labor. Even without the sacrificial system, the Omer still has an eternal message for us.
Passover represents the liberation from Egypt, whereas Shavuot represents the receiving of Torah at Mount Sinai. The Omer is the link between the two holidays (Sefer HaChiniuch). To go from liberation to responsibility: it is something we can all experience as individuals, which can explain why we personally count the Omer for ourselves (Ramban's commentary on Leviticus 23:15). In order to be able to accept responsibility of Torah, our ancestors had to become cognizant of their free will and develop it in a way to serve G-d. We reenact this process by counting. However, it's not a simple act of counting. It is an act of consciousness, a mindfulness that with each day, we get closer to figuratively receiving the Torah.
The freedom that was gained during the Exodus only has meaning because we are able to exert our free will. Our free will provides us with the ability to develop our characters and grow. It is the very thing that separates human beings from slaves. Free will is also the premise behind the Kabbalistic practice of counting the Omer by focusing on the sefirot. Each day during the Omer starkly reminds us that we can ascend upwards with our character development by focusing on something as seemingly mundane as counting and turning it into something divine. Every day during the Omer, we have the potential to take a journey of introspection and spiritual refinement like our ancestors did when they prepared for receiving the Torah at Mount Sinai. In summation, the Omer is a way of emphasizing that each day counts, a lesson we can take with us and apply to the rest of the year.