why is my vote important
Your vote is important because it tells you that you participated in your government. If you voted, you have the right to complain about the elected officials. If you didn't vote, then you don't have the right to complain.
In addition, some elections are won and lost by very narrow margins. If just one additional person voted in each of the tens of thousands of precincts, they'd make a big difference in the outcomes of many elections.