When things don’t go the way I planned, how do I avoid getting angry about it?
If things turn out not the way you wanted, how can you prevent being disappointed and bitter? Listen to me. The חובות הלבבות in שער הבטחון says that הקדוש ברוך הוא, sometimes does that to you, to teach you a lesson. Sometimes Hashem chooses to teach you the lesson that you are not the one who is the author of your fate. To let you know that He’s in charge. So although you made a certain arrangement, and you planned, and you hoped that it would turn out a certain way, הקדוש ברוך הוא is teaching you a very valuable lesson. The lesson that, “I am the מלך.” Hashem is letting you know, “I am in charge, not you.”
So, instead of being disappointed, you should say, “I thank you, Hashem, for that lesson. It’s worth money, that lesson. I really should have to pay for that lesson. Thank you, Hashem.” Because otherwise, you think that you’re the boss. You think that you’re the whole boss. You’re the whole מאכער here. So, הקדוש ברוך הוא says, “No, no. You’re not the מאכער at all. I’m the מעכער.” And that’s why things turn out the other way. Not the way you planned. Hashem is telling you, “I’m the מאכער here!”
So you’re getting a free lesson. And הקדוש ברוך הוא is not charging you for it, so be happy.