Aston Martin began the season as the surprise second-best team to Red Bull, with Alonso scoring six podium finishes across the opening eight weekends of the year, including second-place results in Monaco and Canada.
However, as rival teams have introduced upgrades at recent grands prix, Aston Martin has fallen down the pecking order, with Mercedes and McLaren leapfrogging the Silverstone-based outfit.
Despite this, when asked how he reflects on the season so far, Alonso responded: "Incredible.
"[It has been] a dream first half of the season. We are P3 in the constructors' championship in front of Ferrari, we are P3 in the drivers' championship together with Lewis.
"It was impossible to think this way in Bahrain."
Speaking exclusively to Motorsport.com ahead of the summer shutdown, team principal Mike Krack hailed the "open and transparent" relationship between team and driver.
When Alonso's Aston move was announced, it caused eyebrows to be raised given the stark difference in on-track performance compared to his then-employers, Alpine.
Assessing the success of his winter switch given the current turmoil at Alpine, Alonso added: "You know, it would be nice to have a crystal ball and before you make a decision in switching teams you know the future.
"But yeah, you know, in the end, I'm happy where I am, and there is a project here into the future and I'm very proud."
While the popular belief is that a driver loses their edge with age, Alonso, 42, continues to buck this trend.
But pointing to the recent return of Daniel Ricciardo at AlphaTauri, Alonso stated that youth is not everything in modern F1.
"It [my age] was the theme all through the year," joked the Spaniard. "But no, I think people already saw that you know, it's not a big change when you're 41 or when you're 25.
"It's more in your head, in the motivation, how you approach the weekend. And yeah, races like today or the stars of today, or even a few examples, you know, in other teams - they bet more on experience. Like Daniel now in AlphaTauri and things like that. So it's not about youth, it's just about going fast."
