"For it is impossible for those who were once enlightened and have tasted of the heavenly gift, and were made partakers of the Holy Spirit," (Hebrews 6:4 KJV)
"Jesus replied, "I tell you the truth, you want to be with me because I fed you, not because you understood the miraculous signs. But don't be so concerned about perishable things like food. Spend your energy seeking the eternal life that the Son of Man can give you, For God the Father has given me the seal of his approval." They replied, "We want to perform God's work, too. What should we do?" Jesus told them, "This is the only work God wants from you: Believe in the one he has sent."" (John 6:26-29 NLT)
Well then, after having been through a storm or two, I can see why some people might fall away, but I really can't see how they allow it to happen. There are a couple different ways to look at this: one is to look at it from the human side, as if there was something you can do to control yourself, even though you have been purchased by the blood of Christ; and the other is to consider that it is impossible to get away out from under God's grace!
Personally, I will try to forever stand upon the second one! No matter what I might do, my life is in His hands! That is what I believe and that is what I must continue to stand upon, even if I might fall away, He doesn't allow me to reach a certain point, without bringing back to repentance. Yes, it is totally fine to repent again for sins that we commit, even after we have known better to not do them.
Hopefully everyone should know that, because He put a mark upon us, from which we really cannot stray too far away. I can't begin to tell of all the times I have tried to walk away, if only for a brief me time; but somehow, I cannot hide the mark that He has placed upon me, that makes it hard to hide from the One who owns me!
If you don't know what I mean, it is really not all that hard to believe. When you were saved, your life is no longer your own; you're a child of God, which makes you a citizen of heaven, which now makes you an alien to those of this world. Sorry, but you are stuck in His grip, and He is not letting go...
""My sheep listen to my voice; I know them, and they follow me. I give them eternal life, and they will never perish. No one can snatch them away from me, for my Father has given them to me, and he is more powerful than anyone else. No one can snatch them from the Father's hand. The Father a I are one."" (John 10:27-30 NLT)