‘To go out on a high note’ means to finish something in a spectacular fashion.
For example:
The band went out on a high note by performing an encore including the crowd’s favorite song.
or
The gymnast went out on a high note by performing a triple back flip through a burning ring of fire.
‘To give something a rest’ means to stop doing something for an indefinite amount of time.
For example:
Alan had been doing homework for five hours straight so he decided to give it a rest.
or
Sarah had been annoying her little sister Rachel for a while when Rachel suddenly lost her temper and smacked her in the mouth, at which point she decided to give it a rest.
In this example the music has one ‘high note’ followed by the musical symbol for a ‘rest’; the pun is that the caption says he’ll ‘go out on a high note and then give it a rest’ which is reflected in the music below.
‘To lose one’s temper’ – awaiting meme
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