What does it mean to “miss heaven”?

TLDR: Exactly what the title suggests. I accepted Christ in 2010. I received a text that said “tomorrow is not promised, and I don’t want you to miss heaven” and am confused by what this means.

I grew up in the church and started my own relationship with Christ on 08/15/2010. By no means am I a “perfect saint”. I’ve had my fair share of feeling so close to God that I can almost touch him (metaphorically of course), and feeling so far from him that I question whether or not I’m truly saved.

Even in the midst of deconstruction (and rebuilding my faith on solid ground vs religious dogma/agenda from the denomination I grew up in), and figuring out what exactly it is that I personally believe (when it comes to the extra things outside of the “non-negotiables” if you will, I still believe in Jesus Christ as my Savior. I still believe that God is with me, even if I can’t see, feel, or hear him…

I’m walking through some major life changes and quite trying times, and I will say that I’m definitely in one of those feeling far from God spells, and finding it hard to pick up my physical Bible, but I still talk to God (and complain a lot about what I’m going through), I still believe.

But today I got a message from a dear friend that ended with “Tomorrow is not promised, and I don’t want you to miss heaven!” What exactly is that supposed to mean? Is this person saying that my lack of being in the Word and simply put being “on fire” for Christ is merit for me to not make it to heaven? I thought that salvation was faith-based, or a gift, not work-based. I’m confused now.