The Thinking and Feeling mental muscles are ways of making decisions, or alternative forms of "Judgement".
You need to make judgements very frequently, whether it is a minor decision, such as "shall I get up or stay in bed?" or a major decision such as "do I like this person enough to marry him/her?"
Bad Joke: A young child watched her single mother voting at the polls. As they left, the child said "you voted for someone you loved". The mother asked "why do you say that?". The child replied: "because you put a kiss by his name".