Reason One: Your Vote Matters, Stupid!

Yes, you are just a drop in a sea of people, but do you know what? Everyone else is too! Every vote has the same weight and every vote counts!

There are countless examples in the history of democracy where a result of a national election came down to just a few hundred votes. Just think back to the US presidential election of 2000, when a difference of merely 537 votes in Florida lifted George W. Bush past Al Gore.

Even if you vote is not cast for the winning side, it does not mean that it goes to waste. Politicians are opportunists. If there is a significant part of the electorate behind a certain cause, mainstream candidates and parties are going to pick it up and make it their own. 
Green parties emerged in the early 1980s all over Europe. While not winning majorities, the firm support for an environmentalist agenda caused all major political parties to adopt own programs for environmental protection.

Some countries (not the US, but for example Germany) fund political parties based on their election results. In this case, every vote, even for a minority party counts just for that reason. 

If you are not going to vote, just because you think your vote doesn’t matter, why are you getting up from bed at all? If your vote does not does not matter, why does anything else you do?

Reason Two: If You Are Not Braindead, You Are Not Indifferent!

I understand that occasional making a choice between the available candidates looks like choosing between a rock and a hard place, or like South Park put it so eloquently in 2004: between a giant douche and a turd sandwich.

However, only because you dislike, maybe even despise the candidates, this does not mean you are indifferent to them.
For most national elections, independent websites are offering an easy way to compare your personal political beliefs with the ones of the candidates and parties running. For the US, the best-known page is isidewith.com. It is for sure not perfect, but doing the quiz in true fashion should give you a good indicator with whom among the candidates you share the biggest overlap.
The more questions you answer and the more you rank the importance of the questions to you, the more detailed the result will be.

Alternatively, you can always make your short list of the major issues at your heart and then search the candidates’ programs or screen recent speeches to see how they stand in regards to your causes.

If you are living and breathing human being, there is no way you are truly indifferent between two or more candidates.

Reason Three: Vote, Because You Can! 

Many things in life are completely out of your control but still effect you “bigly”: a giant pimple on your face on the day of your dream date, a grave sickness in your family, a natural disaster or an economic downturn.

While sometimes in life we have no other choice but to suck it up and take what life throws at us, make it a principle to take fate in your hand whenever you can. 

If you follow this simple guidance in life, I am sure your life will be pretty awesome.
It also spares you the awkwardness, if your kids or your grandchildren ever ask you for whom did you vote in that particular election.

Go and vote, because you can! Make a choice because you have a choice!

Is there ever a valid case for not casting your vote? I can only come up with two scenarios in which it would be acceptable to stay absent from an election: 

1)    If the election system is so obviously rigged, that major opposition candidates were barred from running or decided to boycott the election. In this situation, a vote of absence or an invalid ballot might send a stronger signal than voting for one of the remaining candidates.

2)    If voting for the candidate of your choice would put you or your family at risk to facing harm to life or livelihood. Nobody expects you to be a hero.

As neither of this conditions is applicable for the US Presidential Election, it would be truly inexcusable not to vote, if you are entitled to do so.