fall behind

/F AO1 L B IH0 HH AY1 N D/
verb
  1. 1

    To be late (for a regular event)

    โ€œYou're falling behind with the rent.โ€

  2. 2

    To be progressively below average in performance.

    โ€œIt's not like John to fall behind in maths.โ€

  3. 3

    To fail to keep up (with)

Source: https://en.wiktionary.org/wiki/fall%20behind