I am poor at thanking or appreciating people.

I am poor at thanking or appreciating people. It means that I usually find and point out other's mistakes or faults. Actually, I am disappointed with my attitude and try to fix it, but I can't. This morning, I found out that there was something wrong with the ordinary medicine because a farmer said we should be careful when taking medicine. And my wife was the one who cut one of them. it is for next week not today. I found out about it and told her that it was the wrong one and that was right. After a while in the evening, I angrily told my wife that she was wrong with how she cut the medicine in the morning. Suddenly, she was upset and asked, "Why do you emphasize it was my mistake? and Try to find out who really did something wrong." And I felt it was my mistake, and it is not a difficult thing to change ordinary medicine. So I apologized to her, but she was already sad. And tomorrow is her birthday. I need to do something good to her. What is the best one?