Answer:
He meant that he will return to the place where Cassius is, if he cannot physically return, his mind will be there.
Step-by-step explanation:
In the question above, we can see a dialogue between Cassius and Titinius, where Cassius asks Titinius to take a horse and go and observe the troops that are approaching, but to come back with news if these troops are friends or not. At that moment, Titínio states that he will return because his thoughts will always be with Cassius, if he cannot return physically, Cassius will be sure that he will return in thought.