God is good and He does great things.
When Israel crossed the Jordan river on dry ground into the land of Promise they were instructed to take 12 stones from the riverbed and build an altar of remembrance on the shore. This would last generations so the collective memory of the power of God would continue.
By taking time to share what He has done in your life you are building a marker that you and others can look to and remember what He has done. This allows us to know that He will continue to do great things. This gives hope to us now and in the future.