The point does not hinge on earning ones salvation but verses like Hebrews 10:26 if we deliberately continue sinning after we have received knowledge of the truth, there is no longer any sacrifice that will cover these sins. If OSAS were true, such verses would not exist.
A common misunderstanding on display here....you are taking the verse out of context....There are NINE chapters before you get to Chapter 10....The ONLY SIN being discussed is the Sin Of Unbelief...The Jews being addressed in these Chapters now had a choice after the Cross —- Stick with the now obsolete Old ways of dealing with sins( putting your Faith in animal sacrifices to atone for them) or putting your Faith in the Blood Of Jesus to take care of your sins.....the “ willful sin” being discussed is going back to Temple Worship—— Trusting in the Blood Of animals and thereby “ trampling” on the All Sufficient Blood Of Jesus....hope this explanation helps you and many others out there to understand....