Emotions are more choice than you're giving credit for. Next time you notice you're feeling annoyed, take a moment to manage your emotional state. Reflect on your day in the broader context; get to the bottom of what's really bothering you (often you just remember that it's mundane and you get over it); think about something you're excited about; consider changing the topic. Often, with ten or fifteen seconds of thought, you can completely transform an unwanted mood.