To tell the truth, though I won't go as far as to doubt God's existence, I can see a possibility that He does not exist, and there are many times—more and more as of late, it seems—where I find myself frustrated and disappointed by what seems to be God's refusal to live up to His promises in the scriptures.
And therein lies the key. G-d disappointed me. G-d didn't do what I wanted Him to do. G-d let me down. G-d doesn't care. This is the root. It isn't a matter of existence. It is a matter of G-d not living up to my expectations, so out of anger or hurt, I choose to pretend He doesn't exist.
For me, I know G-d exists and that He loves me more than I could ever fathom - a love that goes beyond my understanding. My knowledge of this goes far beyond scripture. My knowledge is based upon my own personal relationship with Him. It is based upon the miraculous transformation He has made in me. When I called out, He answered me and showed me great and mighty things which I did not know. When I took a fearless and searching moral inventory of my life, He revealed Himself to me and showed me all the places He was during those times. He has demonstrated His love for me again and again, showing me always that He wants the best for me.
In our human mindsets, keep in mind that our brains are not our friends. And our human existence is bound by time. G-d does not have these shortcomings. His brain knows all, and He is able to transcend time. I always try to remain cognizant of that. God knows the big picture. I don't. So I make a decision to place my trust in Him. Sure, in my own mindset there have been disappointments. But I am reminded of the hell I lived in before I first uttered that prayer asking Him to reveal Himself to me.
If you doubt G-d's existence, then ask Him to show Himself to you. Your life will never be the same.
Third Day - Show Me Your Glory