"...significantly easier to see in the days before it reaches its highest point in the sky than in the days after."

Copy and paste the following link to your browser window to find out when Mercury reaches its highest point in the evening sky in YOUR location!

in-the-sky.org/news.php?id=20210517_11_100

(The link above shows Washington by default. Once you enter in your location, it will give you information about the days when you can best observe Mercury from that spot on the earth.)

"Mercury reaches its highest point in the evening sky, shining brightly at magnitude 0.3. See it just above the western horizon right after sunset.
...
Since Mercury can only ever be observed in twilight, it is particularly difficult to find when it is in a thin crescent phase. Thus, it will be significantly easier to see in the days before it reaches its highest point in the sky than in the days after.
...
Observing Mercury

Mercury's orbit lies closer to the Sun than the Earth's, meaning it always appears close to the Sun and is lost in the Sun's glare much of the time.

It is observable for only a few weeks each time it reaches greatest separation from the Sun – moments referred to as greatest elongation. These apparitions repeat roughly once every 3–4 months, taking place alternately in the morning and evening skies, depending whether Mercury lies to the east of the Sun or to the west.

When it lies to the east, it rises and sets a short time after the Sun and is visible in early evening twilight. When it lies to the west of the Sun, it rises and sets a short time before the Sun and is visible shortly before sunrise.

However, some times of the year are more favourable for viewing Mercury than others." ~ in-the-sky.org/news.php?id=20210517_11_100

Images
(1) “Mercury at highest altitude in evening sky”
© NASA/JPL/MESSENGER
Link Source: in-the-sky.org/newsindex.php?feed=innerplanets

(2) “The inclination of the ecliptic to the horizon”
© NASA/JPL/MESSENGER
Description:
The inclination of the ecliptic to the horizon changes over the course of the year, affecting how high planets close to the Sun appear in the sky.
Link Source: in-the-sky.org/imagedump/innerplanets/inclination_ecliptic.png

(3) “Planet Orbits”
© NASA/JPL/MESSENGER
Description:
The orbits of the planets Mercury, Venus and Earth, drawn to scale. The orbit of Mercury is significantly non-circular.
Link Source: in-the-sky.org/data/planet_orbits.png

...

Source
The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).