Be wide of the mark = be wrong or miss what you were trying to hit; incorrect or not accurate.

• Yesterday’s weather forecast was a little wide of the mark
• Watch out, the arrow is going wide of the mark!
• I thought I knew what real estate costs around here, but I was wide of the mark.

Do something on the spur of the moment = do something suddenly without planning; on impulse. ( spur= metal on boot which makes horse go faster – related to horse-riding)

• I don’t generally do things on the spur of the moment.
• It wasn’t spur of the moment decision.  We discussed it in detail beforehand.
• I decided on the spur of the moment to invite him.

Be on the cards = be likely to happen.

• An election is on the cards this year.
• It is still on the cards that I’ll get a contract for the job.
• A: So you think they will get married next year.
• B: I think it’s on the cards.