I mean, this is literally what happened, so I don't see why the quote wouldn't be real. In late 1956 the boat coming from Mexico carrying 82 people was supposed to land in Cuba, join other comrades with vehicles and supplies, travel up the coast and connect with even more rebels. Then they would attack and capture the military outpost, seizing guns and ammo, travel to the Sierra Maestra mountains, from where Fidel would call for a general strike and topple Batista's government.

None of that happened. The boat was garbage, they landed days later than planned. By that time other rebels carried out diversions that alerted the army, and Fidel's company was ambushed as they were crossing the marsh after losing the boat and all the supplies with it. They had to split up and run, trying to get to the mountains with no food, water, or medicine (Che Guevara was seriously shot). By the time they reached their destination only a dozen of them remained. And the rest is history.

I don't know if he said this verbatim, but I do know he was at one point thugging it out in forests with less than 20 men at one point in his revolutionary career