It's for everybody....some are a lot more confident in its' outcome...but noone IS CERTAIN.
If you happen to decide that it's not possible to be certain, does not mean it is nor is everyone else required to join you in your uncertainty.
The only reason for uncertainty concerning God's promises is that someone does not really believe God and that He will do what He says He will
IOW, they do not trust God. Therefore, they do NOT have saving faith and have no reason to be certain.
1 John 5:13-15 I write these things to you who believe in the name of the Son of God that you may know that you have eternal life. And this is the confidence that we have toward him, that if we ask anything according to his will he hears us. And if we know that he hears us in whatever we ask, we know that we have the requests that we have asked of him.
Except Mary, folks that Rome considers to be capital "S" saints...