It is the philosophy of Stoicism condensed to three easy, daily rules on how to deal with the world.

Be in Control of Your Perspective (Perception):
Do not allow the emotions or assumptions to take control of your brain. Prefer to look at things optimistically. ST- Never jump to a bad conclusion.

Do the Right Thing (Action):
Put your energy into positive constructive action, now here and now. Be motivated to do good to yourself and other people.

Accept What You cannot Change (Will):
No longer worry about things you can not thrash out such as The weather or The past or opinion of other people. Accept plausibly whatever life presents you with. Find something to feel thankful about it.

In Short: be visionary, full of purpose and content with what life brings regardless of how you can change it. It is all you require according to this philosophy to live a grounded life.