This quote means that it is better not to make an excuse than to make a bad excuse. A bad excuse is an excuse that people will not believe or that is nonsensical. For example, if you are late to a meeting, it is better to just apologize and not make any excuse, than it is to make up a bad excuse that people don’t believe. Making a bad excuse may make people think less of you, whereas not making an excuse shows that you are being honest.