Imagine a room with a clock. The clock reads 10pm.

Imagine the same room one minute into the future where the clock reads 10:01pm.

At 10:01 pm you send a marble one minute back in time.

Now at 10:00pm the room has 1 marble.

What happens at 10:01pm? You send a marble 1 minute back in time.

Now at 10:00 pm the room has 2 marbles. One that was already there, and one that you sent back this iteration.

Each successive iteration of this time loop will add one marble to the room. Assuming the room is infinite, the marbles will condense into a mass eventually collapsing into a neutron star and finally a black hole of infinite mass. All this happens precisely at 10:00 pm so 10:01 never occurs because time as we know it would cease to exist at 10:00 pm.