When smth closes in on you, it approaches you on all sides. It leaves you with an uneasy impression of being squeezed in a corner, or of being surrounded until somehow stuck. Metaphorically, you can say that memories from the past are closing in on you, and cut you off from the present.
To me, something closing in on you carries a negative, almost scary connotation. Usually, we move towards future times, but since the future gathers in on you on all sides, it reclaims you from the present and detaches you from it.
Don't let the future close in on you - means stay in the present, and watch into the future from a (safe) distance.
Troubles, worries can close in on you...
Student or Learner