You will be OK.... it is about being certain, KNOWING that no matter what happens, you will be OK.  

I recently read a story of a women who had been plagued with lumps in her breasts, the last one being discovered while she was still nursing her youngest child. Up until this time, the lumps had been benign, but the worry, the fear, the depression for her each time was debilitating. She projected thoughts of motherless children, grieving husband, and above all she was certain that THIS TIME she would not make it. She was trying so hard to keep herself in check while waiting for the results of the mammogram; with meditation, long walks, praying, anything to try and keep a calm and positive attitude. Finally, early one morning, she was sitting by the lake talking with God about how scared she was, and said "Isn't there any way I could handle this without being so scared?" and that was it. A feeling of calm came over her and continued to expand from that time forward. This was a divine gift! She realized in that moment, that it wasn't about praying that the lump was not malignant, or praying that she didn't have to have her breasts removed, or praying that she didn't die. These are the trials of life, the fear only makes it worse; but if you trust have faith in a higher power and in yourself, you can handle anything. 

It is a KNOWING that if any or even all of these things happened she would be OK. Death has long been the ultimate fear; but it is a KNOWING that we never really die, our souls will just leave this human form and return home. 

I think this knowing comes from trusting yourself, or surviving your worst case scenario, or maybe it's age. But somewhere along the line you settle into yourself, quite confident that all is well, and life is good. The little things simply don't matter anymore, you are finished with all the nonsense, you have formed your own beliefs and feel happy in your own skin. And so with little or no drama you realize that NO MATTER WHAT you will be OK.