I don't totally agree with this. It should be true for personal expenses. If you're going into debt to go on vacation, or buy a new toy, or something then that's a bad idea.

However, if it's an investment, debt isn't bad. Your goal should be to go into debt to fund growth, to then make more back. If it's done in this way, and intelligently, with good knowledge, it is useful. It's still a risk though.