For we ourselves were once foolish, disobedient, led astray, slaves to various passions and pleasures, passing our days in malice and envy, hated by others and hating one another. But when the goodness and loving kindness of God our Savior appeared, he saved us, not because of works done by us in righteousness, but according to his own mercy, by the washing of regeneration and renewal of the Holy Spirit, whom he poured out on us richly through Jesus Christ our Savior, so that being justified by his grace we might become heirs according to the hope of eternal life.
~ Titus 3:3-7 ESV

Remember that prayer that you prayed, or the time you raised your hand during an “altar call”? Yeah – that didn’t save you. Jesus saved you. You’re not good enough to save, you’re not smart enough to have God look at you and say, “I HAVE to have THAT GUY with me in Heaven!” There’s no amount of “good deeds” that you can do to warrant God’s saving work to be applied to your life. If anything, everything you do to “work off” your salvation or make yourself worthy is just an affront to God and mock Him for His work on your behalf. It’s not you who hold onto God, but God that holds onto you. You can’t be lost – you can’t “walk away” from your faith because it’s not “your faith” to begin with. God is the one who started the ‘good work’ of salvation within you and He will not lose a single one whom the Father has given Him. You are secure because of God’s love for you, not because of God’s love of you.