system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do we have more negative emotions when we're tired?
gpt
Because negative emotions generally are the things your brain uses to change gears to not expose you to risks.  When you're happy you're willing to take more risks because you're in a situation where things are good.  You have social support, you know there are other people to help if things go wrong, and you have enough security and safety that if things go bad you're less likely to suffer horribly.  When you feel sad, or lonely or insecure you're less protected against things going really badly.  So you assess risk more harshly, and the possible rewards that would come with some activity are less important than the dangers of failing.  Negative emotions can make you feel tired as a way to conserve energy and not do needless things that will create risk.  Feeling tired means you're worn out going out and doing something is less likely to work out because you've already used up a bunch of energy and you need to recover.  So being sad can make you feel tired and being tired can trigger negative emotions because the negative emotions can prevent you from acting rashly.