If a mistake is likely to be repeated or needs to be corrected, it is important to point it out, but even then do it with finesse. In many situations, the mistake is a one-time error and there is absolutely no need to point it out. If there is a healthy relationship between husband and wife and both have high self-esteem, this is not an issue. But there are many marriages in which pointing out mistakes is the primary focus of communication, and this causes much distress. Don't criticize small and irrelevant mistakes unless you know that your husband or wife will appreciate it.
Some partners constantly correct the other's grammar, choice of words, and patterns of speech.
If you find someone's grammar or pattern annoying, correct it in a way that enables the other person to feel good. Don't do it in a way that sounds like an attack on the intelligence and competency of your husband or wife. I interviewed a retired American Rabbi who settled in Jerusalem, not far from most of his married children and grandchildren. I asked him about the first thought that comes to mind when he thinks about an important principle for marriage. If I don't like something, I consider it dishonest not to express my thoughts frankly and bluntly.