Fate is the idea that what happens is settled in advance and will arrive
whatever anyone does. It is the older and more personal ancestor of determinism, and the two are frequently confused.

Fate and determinism are different

Determinism holds that every event follows necessarily from prior causes. Your
deliberation and effort are part of that chain, so what you do genuinely
affects the outcome — it was simply always going to be what it was.

Fatalism holds that the outcome is fixed independently of the route. Whether
you act or not, the same thing happens. This is the position that makes effort
pointless, and it is far stronger and much less defensible.

The practical difference is complete. Under determinism, going to the doctor is
one of the causes of recovering. Under fatalism, you recover or you do not, and
the appointment changes nothing.

The Greek treatment

For the Greeks, moira was a portion allotted to each person, binding on
mortals and in some tellings on the gods. Tragedy repeatedly stages the
structure in which an attempt to escape a prophecy is the mechanism that
fulfils it — the escape was written into the allotment.

The Stoics gave fate a rational form. The cosmos is an
ordered whole pervaded by reason, and events unfold according to that order.
Their response was acceptance of what is outside your control combined with
full effort on what is inside it, which is a determinist position rather than a
fatalist one. See amor fati.

The idle argument

Ancient critics pressed the objection directly: if you are fated to recover,
calling a doctor is unnecessary, and if you are fated to die, it is useless —
so why call?

The Stoic reply was that outcomes are co-fated with their causes. Recovering
with the doctor's help is the fated outcome, and the call is part of it. This
answer rescues the position from fatalism and is essentially the compatibilist
move about free will.