Tomas goes out to lunch to think things over. He decides that this was the best way for their relationship to end. She came into his life seven years earlier, uninvited, with a heavy suitcase, and she left of her own accord, with her heavy suitcase.
His love for Tereza was a beautiful thing, he knows, but also exhausting. He hated having to hide things from her and apologize all the time.
She did in fact weigh him down; now that she is gone, he is free, he is light, he is in "Parmenides' magic field" and enjoying "the sweet lightness of being" (1.14.8).
And yet, he does not call Sabina, or find another woman to celebrate his bachelor freedom. "Perhaps," surmises the narrator, "he sensed that any woman would make his memory of Tereza unbearably painful" (1.14.8).