God has made promises to His followers (over 7,000 in His word). We may doubt it during dark times, but those times may not be hindrances to the fulfillment, but the pathways. Don't doubt in the darkness what God has told you in the light. He cannot lie and is always faithful to His promises to us!
God will meet us where we are. When we doubt and struggle in faith, God is gracious to come and remind us (again) of His promises. And He is faithful. Promises He made to our ancestors that involve us will be fulfilled! God has rich, personal promises He longs to make and accomplish in our life as we look to Him. He is not limited by time or history. What He has said, He will accomplish.