Why Did I Sabotage My Own Success?

I recently quit my job at the advertising firm where I'd been working for six years. It was a sudden decision, made on a whim during a particularly stressful week when we were pushing to meet an important deadline with our biggest client. The truth is, I've always had ambitions of starting my own agency and felt that staying in this position, even as the creative director, would hold me back from achieving those goals. But here's where things get murky for me: the day before I submitted my resignation, there was an internal meeting about promotions. My colleague Alex, who started a year after me but has always been seen as more likable and outgoing than myself, received a promotion to senior creative director while I remained at creative director level. At that moment, my resentment towards Alex boiled over into something far worse, I decided to sabotage his new position by secretly undermining him in front of the boss during their first project meeting. To be clear, sabotaging someone is clearly unethical and counterproductive to a workplace environment, but part of me wanted to feel like I deserved that promotion more than he did. It's not as if Alex didn't earn it; his work has always been good enough to warrant the recognition. However, there was also an underlying belief in my mind that this company didn’t value my efforts as much because they saw him as more marketable and relatable. The next day I submitted my resignation letter, feeling relieved yet conflicted about what had transpired. Since then, every time I think back to it, a sense of guilt washes over me because sabotaging Alex was not only unprofessional but also an act that didn't align with the kind of professional I want to be moving forward. So, am I the asshole here for my actions? Is there something more deeply rooted in this behavior than just momentary spite or a desire for recognition? And how can one move past such unethical choices to rebuild personal and professional integrity?