No...we can know, and we who have passed from death to life, do know. Just as Jesus said, "we know of what we speak." But those who do not know only speak from that empty reservoir: They do not even know what they do not know.
And passages like "running the race" are not speaking of when "It is finished." But...when "It is finished", we are right to say so--just as Christ did...that is our witness; and that witness is to be the hope of those who follow, and should not be mocked. To mock those who follow Christ in the very things He Himself did, is to mock Christ.
Was Christ "prideful" to say "It is finished?" No! Nor is it pride that we should tell the same truth. But it is against (anti) Christ to speak against those who do. You do it to Him.
Jesus ran His course until "it was finished" and now we must run our course till "it is finished" It is disingenuous to claim Jesus' race as our own...until we have run the course. Jesus said that as He was dying. And we can do likewise if we have remained faithful till the end.
Rev. 3:21 To him that overcometh will I grant to sit with me in my throne, even as I also overcame, and am set down with my Father in his throne.
Jesus didn't overcome instead of us. We must each run our own race. We can't say "it is finished" until it is.