Who are the people who attempts to enter heaven but aren't able?

In Luke 13:22-24 > 22 He passed through towns and villages, teaching as he went and > making his way to Jerusalem. 23 Someone asked him, “Lord, will only a > few people be saved?” He answered them, 24 “Strive to enter through > the narrow door, for many, I tell you, **will attempt to enter** but will > not be strong enough. Source Now my question is this. What is the Catholic understanding of "will attempt to enter". Who are these people who attempt to enter heaven? And who are the people who are attempting but aren't strong enough? I would assume God would help them if they aren't strong enough. (They must be rejecting help) Normal understanding would be all practicing Christians. We all are attempting to be holy. Is it all Christians who can't overcome mortal sins in their life? Is Jesus talking about protestants or schismatics since they don't want to follow the narrow door of the Catholic teaching but still attempting to get into heaven?