No, I can't understand how God could have always existed—but that doesn't mean it isn't true! God is far greater than anything we see around us, and the Bible reminds us that He is "the high and lofty One ... who lives forever, whose name is holy" (Isaiah 57:15).
One reason we have difficulty understanding this is because even time itself was created by God. Before time began, God already existed! This is why the Bible calls Him "the Alpha and the Omega (which are the first and last letters of the Greek alphabet), the First and the Last, the Beginning and the End" (Revelation 22:13). Part of God's greatness is that He is eternal. Unlike us, He had no beginning and He has no end.
The Bible, however, also tells us another great truth about God. It is this: Before time began, He was already preparing the way for our salvation. The Bible says, "This grace was given us in Christ Jesus before the beginning of time" (2 Timothy 1:9). And because Jesus Christ is fully divine, He too is eternal—and that's one reason why we can trust Him for our eternal salvation.
Most of all, never forget that one day over 2,000 years ago this eternal God came down to earth in the person of Jesus Christ. He did this to prove that He loves us and wants us to spend eternity with Him in heaven forever. Do you have this hope in your heart? You can, by giving your life to Jesus Christ today.