To quote the famous philosopher Sarah Connor in Terminator 2, "there is no fate, but what you make." Life's meaning is what you give to it. You create your own purpose. That is for each of us to decide. I know I am still working on my ultimate plan, but doubting your knowledge doesn't mean you have  to revert to things you know not to be true to feel comforted. I wish you luck, as I do myself, with finding our purposes. Life can be difficult, perhaps thats why only the strong usually survive.