Should a Motivational Keynote Speaker Use Other People's Quotes?

Yes and no.

Yes, end on a quote. Great advice.

No. Don't use someone else's quote. Then you are remembered as the person quoting someone else rather than an original thinker.

Being an original thinker will generate you a greater following and give your words more impact.

Here's the thing... it's not hard to create your own quote.

Bring up a great quote that you admire. Quote it. Then add 'You know, that might work well for others but for people like us, if we just change one word it becomes much more effective for us.'

Make your small change. You have now added value and connected your name with a well-known name.

It's a win-win.