According to Macbeth, how long had he lived a blessed life?

after the king has been killed he is basically saying that if he had died before this he would have lived a good life but now the damage has been done and he doesn't feel good about bragging and being proud because he feels lousy and now he's afraid of the king's kids to come after him because he's afraid macbeth knows it's him who has killed him. i think this is the answer

"Had I but died an hour before this chance, / I had lived a blessed time; for from this instant