This app was mentioned in 3 comments, with an average of 2.67 upvotes
https://play.google.com/store/apps/details?id=com.dallol.stoicism
It's got a widget that cycles through different quotes. You can also tap it to get a new random quote. I've got it on one of my home screens, right above the calendar one, so whenever I swipe by it's right there.
Note: I had to reboot after installing to get it to show up in the add new widget selection list.
P.S. principles
I second this, being wanting to tell that search and place some quotes in your home screen (example: Stoicism) or wherever reachable, but seeing that it's already mention the main idea I want to convey. Surprised that I've never heard of the quote, however.
There are many. This is the one with the quote, it also has a nice widget. It's not updated anymore though.
There's also Daily Stoicism and Stoico.