I sold two bitcoin for $250 each a few years ago. If i look back at that now i regret that but in those they I could use the money well so it isn't a big deal right now.
Everyone who are in the market for a long time had similar stories, i never thought the price of bitcoin will be above $2k in the near future, i used to trade when ever the price of bitcoin rallies in the past and would wait for a long time to enter once again as i usually have the patience to make the maximum profit, but the last rally just popped my eyes as i never thought that the price would touch $19k .
Your story is still better than mine. I sold almost half of my coins in 2015, when the prices were around $250 per coin. Just imagine what could have happened, if I had held on to them. As of now, my cryptocurrency holdings are worth just around $30,000. If I had refrained from selling some of my coins four years back, then now my net worth would have been more than $100,000. That amount is not high enough to resign from my full time job and take early retirement, but still I could have afforded a lot of luxuries.
The problem is that no one is ready to believe when an analyst comes up with predictions of $20,000 per coin or $50,000 per coin. Because we tend to compare Bitcoin with other assets, such as real estate, stocks and equities. In the stock market, although 100x or 200x rise in a single year (similar to what happened with Bitcoin in 2013, and again in 2017) can occur once in a blue moon, it is extremely rare. So we believe that with the cryptocurrencies also, such rise is not possible.