I've often said that forgetfulness is a great contributor to failure in many areas of our Christian lives. Unfortunately, forgetfulness is not an acceptable excuse:
There hath no temptation taken you but such as is common to man: but God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it.
God did a great work in the life of Joshua toward the children of Israel in demonstrating that the one true and living God was among them and that he would drive out the inhabitants of the land from before them.
And it shall come to pass, as soon as the soles of the feet of the priests that bear the ark of the LORD, the Lord of all the earth, shall rest in the waters of Jordan, that the waters of Jordan shall be cut off from the waters that come down from above; and they shall stand upon an heap.
Now, to escape the tendency to forget, we find in the very next chapter that God commands Joshua to take a man of each tribe and have each carry from this heap, a stone upon their shoulders and leave it in their lodging place that night. Later, these stones were to be moved to Gilgal and set up as a memorial.
And he spake unto the children of Israel, saying, When your children shall ask their fathers in time to come, saying, What mean these stones? Then ye shall let your children know, saying, Israel came over this Jordan on dry land. For the Lord your God dried up the waters of Jordan from before you, until ye were passed over, as the Lord your God did to the Red sea, which he dried up from before us, until we were gone over: That all the people of the earth might know the hand of the Lord, that it is mighty: that ye might fear the Lord your God for ever.
In the churches I've been in, we have times designated for sharing both praises and prayer requests. These are normally printed from week to week to keep track of everyone's requests, but if we're honest with ourselves, we can all think of times we've held back from sharing something because either we felt it wasn't "worthy enough" to be added to the list or perhaps it required a certainly level of confidentiality and we just said, "I have an unspoken request, please."
Nevertheless, God wants us to remember what he's done for us and not to forget. As shaping our lives, our future, and our identity in Christ, he also wants us to pass these testimonies on to our kids to the intent that they might seek him in their own lives and come to know who the one true and living God is and that he too can be their God and they can be his people if they simply accept Jesus Christ as their personal LORD and Saviour.
Consider keeping a journal (electronic or handwritten) exclusively for recording testimonies; nothing more, nothing less. Leave it out in the open somewhere, and be prepared to share its entries whenever an inquisitive mind comes along. Others need not contribute to it; they are your stones of remembrance, but it will inspire others to seek the LORD in their own lives and do likewise.
Blessed are they that keep his testimonies, and that seek him with the whole heart.