From the fruits of true belief in al-Qada wa al-Qadar is that once anything has already happened, we do not doubt that it happened as it was supposed to. So, one never says, it wasn't supposed to happen this way. Rather, once a thing has taken place, we know and believe that it happened as it was supposed to. Thus the saying, قدر الله و ما شاء فعل, meaning this is from the Qadr of Allah, and He does whatever He wills.
Source: Received in Whatsapp message