Deuteronomy 31:8 (NIV)

God could have chosen other ways, but He decided that we should believe — as long as we still live here on Earth.
We believe, we don’t see yet.

“For we live by faith, not by sight.” (2 Corinthians 5:7; NIV)

And we can be sure that what God is telling us is happening. The Bible is the proof. God cannot lie. What we don’t yet see with our physical eyes will manifest. Because everything that God says, happens exactly the way He promised. Let’s not forget: God only had to speak and the entire universe was born.

What does God say?

This: “The Lord himself goes before you and will be with you; he will never leave you nor forsake you. Do not be afraid; do not be discouraged.” (Deuteronomy 31:8; NIV)
You, too, should say (!) the above promise. Whatever situation you may be facing, God is with you and goes before you. You will never be alone.
And believe it. Because it happens to you according to your faith.

And when doubts arise?

It would be surprising if that were not the case, because devils and demons are trying their best to torpedo our beliefs.
Then say it again.