Infidelidade translates directly to "infidelity" or "unfaithfulness". It's a strong and emotionally charged word that immediately conveys the central conflict of the song.
In the context of
"Coisa do Destino" is a heartbreak song about choosing to move on after being betrayed. The singer opens by calling the breakup fate: he suffered, but he is finding a way forward.
The verses describe the wound left by his partner's infidelity. He talks about the dreams and plans he had for the two of them, now set aside "for later," a way of saying they may never happen at all.
The chorus captures the messy pull of a breakup: she keeps calling, torturing him with the same push and pull of ignoring him one moment and wanting him the next, and it makes him cry. Even so, he tells her he wishes her well despite what she did, while asking her to finally let him go and stop trying to reach him.
It's a song about the difficulty of truly closing a chapter: wanting release, still feeling pulled back, and choosing kindness over resentment on the way out.