Is there a word for saying something in a nice way without saying it?

So, you are walking all day with a friend, you feel tired, you don't want to say: "I'm tired, let's stop", but say: "Oh dear, we've walked a lot today".

A friend promised to meet you to go for the football match at 9pm. It's 9 and you don't say: "You forgot the match right?", but for example: "Enjoy your dinner".

What's the word to describe these situations? Not sarcasm, because that is in a negative scope. Can we call it "rhetoric"?

Example, if the friend answers: "Oh thanks mate" and he really forgot, you would want to say: "'Enjoy your dinner' was ______".

Euphemism - a mild or indirect word or expression substituted for one considered to be too harsh or blunt when referring to something unpleasant or embarrassing.

Try diplomatic.

Diplomatic adjective 1.1 Having or showing an ability to deal with people in a sensitive and tactful way - ODO

Here are more words contributed by @TheNate (thanks!):

• thoughtful, kind - these relate more to the character of the person; and
• tactful, gracious - these relate more to the choice words and manner of communicating them.