Subdivision
Subdivision is feeling the smaller notes even when you're not playing them. On a held half note, "& 2 &" is still ticking inside your head. Just before a run of sixteenths, you're already feeling "e & a". The beat stops being a single point and becomes a little grid you drop the notes onto.
It is the single most useful anti-rushing habit there is, and it costs nothing but attention.
Fill the long note
Feel it before it arrives
Two speeds of subdivision, same beat
In a real phrase
The end of Ode to Joy's first line: three even notes, then a longer one. The long note is where players rush the next entry — so subdivide it.
The usual mistake
Rushing the instant the notes get shorter — a fast run, a string of sixteenths — because the pulse was being felt in big empty whole-beats with nothing inside them. And the mirror image: clipping a long note short because nothing was being counted through it. Subdivide, and both problems disappear.
Try
Clap a slow steady four. Whisper "e & a" on every beat while you clap only the numbers. Now play any Stage 1 tune and keep that whisper going underneath — you'll feel where you were rushing before.