We had been working so hard, after the end of the war. For 60 years.
The richer we became, the happier we become.
But at the end, we didn't get happy, however hard we worked.
Would you say so?
The richer we become, the happier we become. (This suggests that this is what happens to people when they get money. "We" here can be read to mean "Human beings")
The richer we became, the happier we became. (Here, "We" suggests specific people. The writer of the sentence and someone else or some other people, and it is a statement of fact. The writer is saying that this actually happened in the past.)