Every time my spouse forgets or makes a mistake, I immediately assume it was deliberate. How do I change this thinking?

Treating every mistake as deliberate poisons the heart and turns the home into a court that never adjourns. Allah reminds us: “Avoid suspicion as much (as possible): for suspicion in some cases is a sin” (Surah al-Hujurat 49:12). Before judging, first assume the good possibility, because forgetting and making mistakes are ordinary human traits. Ask calmly, not accusingly: ‘I noticed this wasn't done, is something up?’ If it really was carelessness, discuss how to avoid it, rather than blowing it up. Save your energy for issues that truly matter. Thinking well of each other makes the home a safe place to be an imperfect human being. See communication & emotions.