Emotional stress is one of the biggest thing that could actually affect anyone when gamble because you would need every part of your brain to be functional and active when playing and that's why even a simple glitch in the focus of mind can lead to so many errors while gambling and even mistakes so it's better to gamble when refresh and relaxed because you would be thinking straight and not doing crazy things just to get at the winning that might be getting so hard to come.
Emotional stress can definitely lead to poor gambling decisions. It's necessary to be in the right mindset and have a clear mind when playing, because a single mistake might have serious effects. Emotional stress can cause not only flawed bets, but also overspending or unsafe behaviour. This is why many experts recommend taking breaks when gambling and not playing when you are upset, angry, or frustrated.