Alonso impressed in Shanghai by beating the McLaren and Ferrari cars to third in Q3, the best-of-the-rest spot behind the dominant Red Bulls of polesitter Max Verstappen and Sergio Perez.
But Alonso admitted that he considered aborting the final lap that pushed him up the grid after slipping up through the complex starting sequence of the Shanghai circuit, which made him lose a couple of tenths.
"In sector one I had a moment in Turn 1 and 2 and I nearly lost the car," Alonso said.
"And then I said: 'Okay, I keep going or I abort the lap? Because I lost like two-tenths in two corners. But we didn't give up, we kept pushing all through the lap and set a good lap time."
The Spaniard said his Aston Martin squad had used the re-opening of parc ferme, a new addition to the revised sprint weekend format, to make further car tweaks that he hopes will pay off in Sunday's grand prix.
But he conceded the ever-changing track conditions made some of those set-up changes a coin toss for the team.
"I think the car did improve since this morning, we made a few set-up changes. Let's see tomorrow if we can translate that into good points," he explained.
"You cannot change the car completely because you are into the rhythm of the weekend, but you can still make some small setup changes.
"Some of them are just for balance problems, but some of them are just guesses that you do into tomorrow's race and you flip the coin.
"Until tomorrow afternoon we will not know the answer, but I'm extremely happy, proud of the team.
"We are not giving up. We are not in the position we want yet but we keep pushing."
Alonso was also in contention for a top-three result in Saturday morning's sprint but retired after sustaining a puncture while fighting Ferrari's Carlos Sainz.
The incident landed him a 10-second post-race penalty, despite the two-time world champion already having exited the race.
