thanks for the email. Can I ask why you are asking? Are you thinking of rejecting the Lord? No, didn't think so. The question, for me at least, isn't so much 'could a born again child of God reject God and lose their salvation' (which I assume is where you are leading) but 'would a born again child of God' do that? Do we have that freedom. Yes. I could yell out at the top of my lungs right now that I hate God and reject Him. Would I do that? No. Why? Because His Spirit lives in me and has poured the love of God into my heart. It is God who works in believers both to 'will and to do'. That is, He is at work in my life conforming me to His will.
But maybe there will come a dark day when everything is collapsing around me like it did Job. And let's say, for the sake of argument, I even start to doubt my faith and God. I might even yell out to God, in my freedom to do so, that I reject him. Do you think God would abandon me because of this? I certainly don't. No, I believe, from the Bible, that Jesus will lose none of those that the Father gives Him (John 6:39), and that 'he who began a good work in you will carry it on to completion until the day of Christ Jesus' (Phil 1:6) I believe that God would carry me, and not forsake me, even though I went through this time of madness. And He would bring me back to my senses. He has big shoulders and He will never 'leave not forsake' His children.
There is more I could say, especially concerning apostates who do totally deny Jesus, but I have written about these in other studies. Possibly look at the study on Eternal Security part 2 - some of those 'but what about' passages. Especially concerning Heb 6 and Heb 10.
Hope this helps, and may God bless.