Has not following your rules cost you money? I lost 4k today

I was getting a little bored of the process so on Friday i threw a pretty sizeable amount into SPY just as a "eh if it goes up ill make a few hundred or lose a few"

Enter deepseek which sent the markets down alot, i ended up selling for a 4k loss

So for the rest of the day ill be thinking what a fool i am...Anybody else have stories like this? i cant be the only fool