To make friends, you must be honest and keep your promise. This sentence expresses the importance of honesty in making friends and the value of commitment. It means that in the process of making friends, you should always be sincere and trustworthy, and don't break your word or break your promise easily. Once we make a promise, we should try our best to realize it, and don't change or give up easily. This kind of values is very important in interpersonal relationships, because it helps to build trust and stable relationships.