if the shoe fits

act one's age, not one's shoe size

Synonym of act one's age (“to behave in a mature manner; to avoid being childish”).

as ever trod shoe-leather

As ever existed or lived.

fits and starts

Activity which is intermittent, variable in intensity, and prolonged by interruptions.

if the shoe fits, wear it

If a description fits, it is probably the case; if an insult accurately describes you, you must bear it; if you take offence at an insult that was only implicitly directed at you, you admit the insult is true enough to be recognizable.

pebble in one's shoe

A small and bothersome issue that may worsen over time.

put the same shoe on every foot

To attempt to apply a single solution to different problems.

soft shoe

A speech, explanation, sales pitch, or other set of remarks delivered in a restrained or conciliatory manner in order to persuade, distract, or otherwise influence someone.

the shoe is on the other foot

The roles of people in a situation have been reversed, such that the advantage has shifted to a party which was previously disadvantaged.