Which is ironic, because the Wikipedia page you just linked to says that "95% of former smokers who had been abstinent for 1–10 years had made an unassisted last quit attempt", with the most frequent method of unassisted quitting being "cold turkey", about which it was said that:

wedrifid is asking for P(success|attempt), not P(attempt|success), and so a high P(attempt|success) isn't ironic.