It refers to honest and straightforward words, and it refers to straightforward words with the nature of exhortation. Because it is straightforward, it often sounds unpleasant, even embarrassing and unacceptable. However, if you accept "advice", it will make people think deeply, warn people and make them forge ahead. As people say, "advice at the most unpleasant time is good for action." However, because "suggestions" are generally unpleasant and unacceptable, the effect of suggestions is often discounted. Therefore, the author believes that putting "suggestions" mildly may be more conducive to "doing".