Missing Riddle

I never knew what I was missing until I had it. Then when I no longer had it, I really missed it. As time passed, I realized that my life was fine before I knew what it was that I was missing and life would be fine again. Then something happened to make me think that what I thought I had was not really what I think I'm actually missing. So, am I really missing something? Yes, some days I do feel as though I'm missing something, but perhaps it's just a feeling, and in actuality, I'm really not missing anything at all!