The safest person to be is you. You can know with absolute assurance from His Word that God the Father is in love with you. God is pursuing you. God wants to save you to the uttermost. He is telling you that no weapon formed against you will prosper. God has promised to make everything that has every happened to you or will ever happen to you to work together for your good. God has promised that He has good plans for you to give you a future and a hope. God has promised to bring you into eternal happiness.
These things you can know with full assurance will be yours because He has said that all who call on His name will be saved (Romans 10:9)—and you can know within yourself if you want His salvation enough to keep calling on Him! But you cannot really know that about anyone else. You can believe for others; you can hope for others; and you can be pretty certain about some—but the Father is primarily telling you about your salvation and only secondarily telling you about others. That is why we are told to keep encouraging one another and praying for one another—we are not to take anything for granted.
The perseverance of the saints is a matter between you and God, first and foremost. And the only thing that really matters is this: do you really want His salvation? He has promised to always love you, to always be forgiving of you, to always be eager to save you to the uttermost—your part is to keep calling on Him to help you in every way that He shows you that you need His help. You do the calling and clinging—He does the heavy lifting!