The Moon is actually larger at certain times in its orbit than at others. When it is closest to Earth in its elliptical orbit it is larger than when it is farther away. But unless you photograph it or otherwise measure it you probably won’t be able to tell the difference since those times would be months apart and you wouldn’t remember how big the first Moon was by the time the second rolls around. To illustrate this photograph a first quarter Moon at aphelion and a last quarter Moon at perihelion (or vice verse) with a fixed focal length lens (so you are sure that the focal length is the same for both pictures) and have each frame printed the same size and compare them. (And just to make it even more variable the perihelion and aphelion distances are different on each occurrence so we get the almanac notations for largest full Moon and smallest full Moon of the calendar year.)
And on any given day the Moon is bigger when it is higher up in the sky than when it is on the horizon because it is closer. You can prove this by drawing two concentric circles, the inner representing the surface of the Earth and the outer the orbit of the Moon, and placing a dot on the top of the inner one [you standing on Earth] then draw a line to the outer circle such that it just touches Earth off to the side [the horizon] and measure that distance, the rising or setting moon. Now compare it to the distance measured straight up overhead [a line from the center of the two circles through your location and extending to the outer circle where the zenith would be but only measure from Earth to the Moon’s orbit] and you will see that the distance from your location to zenith is less than to where the Moon would be when viewed when it is rising or setting so it is actually biggest when it is highest in the sky. But the Moon Illusion effect mentioned above will convince you that the opposite is true.