Regarding quotes in general - I think the very fact that they are being quoted is because they have inspired people. I also think, that in some cases, changes to the words in a quote are made to perhaps clarify to another the inspiration gleaned, or feeling evoked in the 'editor' by the original author.
Here are some quotes from a book I read some years ago by Richard Morgan - he writes Science Fiction (the name at the bottom of the quote is a character within the story).
I hope no one is offended by the language. I typed these up after I read the book as I found these quotes (I think the character was a leader of some resistance movement or rebellion) so I am not 100% if they are correct. I did find them interesting =)
"Face the facts. Then act on them. It's the only mantra I know, the only doctrine I have to offer you, and it's harder than you think, because I swear humans are hardwired to do anything but. Face the facts. Don't pray, don't wish, don't buy into centuries-old dogma and dead rhetoric. Don't give in to your conditioning or your visions or your -flicked--up sense of.. whatever. Face the facts. Then act."
Speech before the Assault on Millsport
"The difference between virtuality and life is very simple. In a construct you know everything is being run by an all-powerful machine. Reality doesn't offer this assurance, so it's very easy to develop the mistaken impression that you're in control."
Ethics on the Precipice
"In any agenda, political or otherwise, there is a cost to be borne. Always ask what it is, and who will be paying. If you don't, then the agenda-makers will pick up the scent of your silence like swamp panthers on the scent of blood, and the next thing you know, the person expected to bear the cost will be you. And you may not have what it takes to pay."
Things I Should Have Learnt By Now VolII