What would you consider a lesson to be taught, in today's world?

I never know. A student I am. The lessons are continuous and change form constantly.

I believe an open mind and an open heart are good to have.

Since your question looks for only one lesson I would limit myself to your query status.

The value of humanity is falling apart too rapidly in today's world as a result of which so much of violence world wide. What we need to teach is to ask to respect social bindings and human values specially to the upcoming generation. Other positive things would follow automatically.

That we are connected and that every problem we face stems from bad relations between us. If we want to change something, and we all know that we should, then we should pay attention to that fact.

Please read the articles below, they give you an exquisite understanding of a very important lesson to be taught in today's world.

Don't trust today's Politicians. Lesson Learned.

That being a Christian does not mean letting someone walk all over you/use you. You need to stand up for yourself and walk away from a volatile situation. God wants us to treat our bodies as temples. Whether that's physical or emotional.

That's my lesson for the day.

In God We Trust. All others we Monitor!

My grandmother had a good one ... Don't believe anything you hear and only half of what you see.

Edit: Bet, Sorry I don't look at others' answers before answering myself. What is it they say, great minds think a like.

I think, There is No Interest In Me, to Persuade the Humans, to "LISTEN" to My Teachings.

Tuck well before zipping up

Live each day as if it were your last.