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I think i know what you mean. Some teas are already relaxing if you drink them! Or pushing you forward, like green or white tea.

Does green tea give you energy? I did not know that. Maybe I shall try some sometime.

It does! But its important how long you let it sit in the hot water.

Why because that makes it stronger?

It changes the effect. More duration - calming effect. Shorter - you get energy

That is interesting, I would have thought it would be the other way around.

Nah, but google can explain you better why and how.