Where did the quote in the details come from, and please talk a little bit about what it means?

Tennessee Williams.

The best things to fight for are the hardest, seemingly “impossible” things to win.

Edit: No clue if it is Williams, I googled and 3 different people supposedly said this quote. Darrow, Churchill, Williams. Who knows.

I think it came from the old movie “Mr. Smith Goes to Washington” with Jimmy Stewart.

https://www.americanrhetoric.com/MovieSpeeches/moviespeechmrsmithgoestowashingtonendfilibuster.html

But I also found that it may have come from Clarence Darrow, as you mentioned. Until I did a search and found it is misattributed to him. They say it came from an author in 1936 and was used in the Mr. Smith movie in 1939

https://en.wikiquote.org/wiki/Clarence_Darrow

It was used again in the movie Darkest Hour about Winston Churchill

https://intellectualtakeout.org/2022/08/riding-the-underground-with-winston-churchill/

The things that are most worth doing (from a certain point of view), are the things that aren’t likely to get done unless the specific person choosing to undertake the task of doing them, does so.

Otherwise, someone else is liable to do those things, so they will get done whether that person chooses to do them, or not.

And some of the least likely things to get done, are ones that most people think are impossible to do.