Within the church there are two competing ideas. One says you cannot lose your salvation; if a person appears to walk away it only shows they were never saved in the first place. The other says you can lose your salvation. (These Christians typically quote verses in an effort to prove that they are saved. But even though they quote those verses they cannot guarantee that they will not fall away.)
There is a third way, which is the only way that a person can have absolute assurance that one day they will enjoy perfect intimacy with God. (And by that I mean they will know the kind of intimacy Jesus knows with his Father in Heaven.)
The only way you, or I, can have perfect assurance is to know that we belong to God. I belong to God, and so do you. He made us and he loves us. He will never give up on any of us.
“But what about those who don’t follow Jesus?”
It is true that many are hostile to God; they don't believe that Jesus died for them. But that does not change the fact that they belong to God. He made them and he loves them. He will never give up on them. But they cannot enjoy intimacy with him or know the peace that passes understanding while they don’t know they are unconditionally loved.*
When we know that one day all will freely choose to worship God, we have perfect assurance and know the peace that surpasses understanding. (If you are not certain of this, I highly recommend reading The Inescapable Love of God by Thomas Talbott and Grace Saves All: The Necessity of Christian Universalism by David Artman.) You don’t have to believe that Hell is eternal to enter the kingdom of God; don’t be afraid to examine this issue.
*Nothing you say or do can change the fact that you belong to God. (See David Artman's podcast The Transactional Approach. See also Artman's book, Grace Saves All. A sample from his book can be read here.)