Enganar means "to deceive" or "to trick." It's a versatile verb that can refer to misleading someone, cheating, or even fooling oneself.
In Tim Maia's song, he sings, "E não vale a gente se enganar" (And it's not worth us deceiving ourselves). He uses this word to emphasize the importance of honesty in a relationship, urging both parties not to pretend or mislead each other about their feelings, especially when the love is gone. It's a key word that drives the song's theme of confronting the truth.
Tim Maia sings this one like a man who has rehearsed the breakup speech and is finally saying it out loud. He opens with "Há muito tempo eu vivi calado" ("For a long time I stayed quiet") and then "Mas agora eu resolvi falar" ("But now I've decided to speak"). The whole song is that moment of finally saying the thing you had been swallowing for years.
The verdict never wavers: "Com você não posso mais ficar" ("I can't stay with you anymore"). He is not angry, just done, laying out the reasons like a checklist: "Toda verdade deve ser falada" ("Every truth has to be told") and "Não tem mais jeito, tudo está desfeito" ("There's no fixing it, everything has fallen apart"). By the last verse he has stopped arguing and is just repeating "Juro que não vou" ("I swear I won't"), a vow aimed at himself as much as at her.