Copying content from other places on the internet,
even if it is your own, actually hurts your site.
Having content that can be found somewhere else on the web actually hurts the rank of your site. Why present a site in the search results if someone has already said what you are saying? Google has a strong preference for original content.
Your content needs to be original.
There is no point in copying content from other places on the internet. If you already have a site (and plan to keep it running) then don't use the same words and phrases even if you are presenting the same topic. Find a new way to say it. You will find that your content actually improves because you have had a chance to think about it more and present it in a way that is even easier for your reader to understand.