I don't understand the existential anxiety about personal salvation. If God saves me and brings me to Heaven, he saves me. If he doesn't, he doesn't. That's ultimately his prerogative and utterly beyond my control. To echo the words of Joan of Arc, “If I am not [in God's grace], may God place me there; if I am, may God so keep me. I should be the saddest in all the world if I knew that I were not in the grace of God."
I don't want to worry about scoring points with God. Even people who say "The Sinner's Prayer" still stress out about whether they really meant it. There's no peace in that. There's no benefit to someone who only acts good and religious because they hope to earn Heaven, or who says a prayer to Jesus and has faith in him simply to avoid Hell. They are mercenaries and opportunists, or at best hired workers and self-interested servants who are expecting benefits and wages. Deep down, they always think they are owed something. They are restless, even while they preach security and certainty. In my experience, they see love with God, and with other people, as transactional. There is always a give-and-take with such people. But our Lord says, "No longer do I call you servants, for the servant does not know what his master is doing; but I have called you friends, for all that I have heard from my Father I have made known to you" (John 15:15).
That's the key to experiencing salvation - God calls us friends. Everyone who seeks him, who is called by him, he regards as a friend. Listen, Jesus will save you because that's just what friends do. Friends help each other. If you want to have "eternal security" in your salvation, you can only find it in friendship with Jesus, with God.
Do you think God does good, or asks you to do good, because he gets something out of it? No, he doesn't need anything. He's God. Goodness, truth, and beauty are what we were made for, and they're what God already is. We are healed by religion rightly pursued for the sake of friendship with God, because we want to grow and thrive in goodness, truth, and beauty. We are each made in the image of God, we are each a living work of art that expresses some aspect of the most wondrous being there ever could be, and we are called to become more and more of who we truly are - the priestly presence and masterwork of God in created matter. We are spirits made flesh, breathed into being by God's Spirit. How mind-boggling is that?
Why then, should any of us worry about avoiding Hell? Or about earning Heaven? "There is no fear in love, but perfect love casts out fear. For fear has to do with punishment, and whoever fears has not been perfected in love" (1 John 4:18). Dwell then in the love of God and have no fear. He has come not to condemn you, but to save you; not to destroy and punish, but to forgive, rescue, and heal.