Bowie's character in the song, who has ended the relationship either actively ("I should have kept you") or passively ("I should have tried"), concludes that he will survive while harbouring feelings of love, loss and regret.
The protagonist in Bowie's song, who has either ended or allowed the relationship to fizzle out, arrives at the realization that they will survive despite still being emotionally invested in love, loss, and regret.