The moon isn’t smaller during a new moon. You just can’t see it from here yet.

Invisibility is not absence. A thing can be entirely intact while nothing about it is available to you, which is a hard distinction to hold when the evidence of your own eyes says otherwise. This applies to your own abilities in a bad month, and to progress that is genuinely happening below the level you can observe.

When you cannot see something you know exists, resist the conclusion that it has gone. Check from a different angle, or wait for a different week. Ask someone who has a view you do not. The view changes more often than the thing does.