On day 27, I am thankful for grace. I totally missed out on the concept of grace for most of my life, and I still don't have all of the answers, and never will on this earth, but maybe it is a learning experience.
I don't believe in once saved, always saved. Neither do I believe Christians regularly sin. If you do, maybe your definition of sin is different than mine.
For years, and in part to my low self esteem, my self hatred, and because of sermons that preachers with good intentions preached; grace was a foreign concept. I believed I had to beg and convince God to forgive me, and that He was just waiting for me to mess up so He could toss me out. I thought if I did sin or fail God in some way, I had to get saved all over again, and beg and beg Him to forgive me.
I have come a long way with my beliefs about grace and forgiveness and about God's love. I still don't have it all figured out, and a part of me still fears I'll never be a good enough Christian to enter Heaven, but I now know God is waiting to forgive, and all it takes is a prayer. I don't believe once saved always saved, but don't believe if you sin, you have to get saved all over again, but you should repent of that sin immediately. There are some who believe future sins are forgiven. I don't, but I do believe God will instantly forgive, no matter how many times or how often we fall in that area.
That is grace. And I am thankful for it.