Perhaps the most personally validating evidence for the existence of God is what are known as near death experiences(NDE). Very strongly personally validating, but not proof of God. But, examine them, and what they tend to share is components generally reflective of what have been described as spiritual experiences, described as such both across time and cultures. One might argue such experiences, be they precipitated by an NDE, or by other altered states, are foundational to the development of a belief in God. Such experiences may be attributed to elevated DMT levels in experiencers of such phenomenon. I.E., we can attempt to blame brain chemistry for the development of a belief in God.
But none of the rationalizations or theories that assist in explaining NDE's will likely make a jot of difference to the experiencer, who seems to be as convinced of God's existence as they ever have been, or ever can be, as a result of the NDE. As well as absolutely convinced of the continuation of consciousness after death.
Of course, these do not prove God exists. But, one can go either way. Even if attributing spiritual experiences to brain chemistry, and acknowledging that NDE is just that, "near", not a permanent state, these people are revived afterall, if you cannot shake the "personal validating proof of God" of the experiencer, there remains the possibility that the spiritual experiences, that are often profoundly transformative to the individual, are exactly as they believe it is. An experience of a higher state of existence, possibly preceding and following biological existence. And many describe the level of Love they experience in that state as being of the nature of God, as what we have traditionally ascribed to and called God, by many names.
NDE's have convinced even atheists that God exists. Which proves nothing, but is, at the least, an odd consequence of coming close to death. And with modern resuscitation, more people are reporting NDE's.
https://www.nderf.org/Archives/exceptional.html
