Am I an irrational voter?

I woke up on Tuesday morning having already decided that I would be abstaining from voting in the 2018 midterm elections. An hour or so later I found myself in my car driving back to Northern Virginia to cast my vote. It ended up being about a 5 hour round trip. Since I was previously planning to abstain, I had not requested an absentee ballot, registered to vote in-person absentee, or registered locally in Charlottesville. I'm somebody who thinks that they have very strong political opinions. That being said, the Senate race in Virginia was seemingly very one sided, and I strongly disliked both the D and R candidates in that race. My congressional district has been a very unchanging blue seat for years. There was little to no hope that my vote would impact either of these elections in my favor. What was it that changed my mind? What flipped the switch of apathy to the civic engagement setting?

Did I really want an "I voted" sticker? Did I want some sort of moral validation? Did I want to make the huge trip and skip my classes in angst just to spite Professor Coppock and the voting model he showed us? The model goes as such: E[MB] + D > MC. It's difficult to prove that my expected marginal benefit of a favorable outcome in either of those races was a high number, considering my previous commitment to abstention, and the knowledge that my vote would mean next to nothing effectively. My marginal cost in this situation was enormous. 5 hours out of the day that I could have spent studying for an exam the next day, THREE classes skipped, gas money, you name it. The cost of this voting excursion was quite large. The ONLY way that I made a rational decision is if D is larger than MC, but given how large MC was, I better have had a darn good reason for having an even highly valued D. Now I honestly don't know what pushed me to make the decision that I made-- it certainly wasn't the barrage of Facebook posts and tweets urging young people to have their voices heard. I believe it was a combination of several things: the Expressive Value of standing on my moral high ground of taking such a large burden upon myself to vote, the heightened sense of superiority to my peers in sharing the story, a bomb opportunity to write a killer blog post, fear of viewing myself as a political hypocrite, saving the babies, and possibly even seeing my dogs and having the chance to take my mother out to lunch. Am I irrational, or do I just have a wacky system of valuing my time and actions?