Although I was exposed to the JW's by my mother as a child, I didn't join until I was an adult. At the time I joined, I was in at a low point in my life and in need of serious help for some psychological issues. But the well-meaning soldiers of Watchtower assured me that the distress in my life was caused by Satan and his world and all I needed was "the truth." I actually had thought, before meeting with JW's, that God had saved me from taking my own life and was guiding my life. Rather than tell me "You need help," the JW elder that started a study with me convinced me that God does just what I thought He was doing and that "He" must have led me to "the truth."
With that background, I can answer your question, "How do I feel about the time I wasted being a Jehovah's Witness?"
20 years after I should have gotten help, I got help. I put a band-aid on a serious problem for 20 frigging years. Watchtower even discouraged the type of counseling I should have gotten. I absolutely hate this dangerous mind-control cult for wasting all that time.
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Edited to add:
minimus I do think that even if we felt like we wasted our time, there's still time left to salvage and enjoy life, right now.
I have to agree. My true personality shown through during my 20-year delay and it wasn't all misery. And now that I got away from Watchtower, I embrace the big and small joys in life. I totally enjoy sharing time and energy and thoughts with others who have their own JW-stories. That's why I spend too much time on this forum and why I meet up with other ex-JW's on a regular basis.