Peter out
To gradually become smaller, weaker, or less before stopping or ending. Their romantic relationship petered out after the summer.
Jack of all trades, master of none
A figure of speech used in reference to a person who has dabbled in many skills, rather than gaining expertise by focusing on one. The shortened version “a jack of all trades” is often a compliment for a person who is good at fixing things, and has very good broad knowledge.
All work and no play makes Jack a dull boy
People say this to warn someone that they will not be an interesting person by working all the time. If you talk about females it changes to “all work and no play makes Jill a dull girl”.
Jack the Lad
A very confident young man who doesn’t take life seriously and doesn’t care much about other people.
Her first boyfriend was a bit of a Jack the Lad.
The sentence is used in a rather negative way to mean ‘anyone’.
You need to send invitations. We don’t want any old Tom, Dick and Harry turning up.