the very concept of looking at past Bitcoin price with a sense of regret of not buying earlier enough or a thought that if you had bought Bitcoin at the time it was at a certain price, you would have been in a certain percentage of profit is a mediocre way of reasoning because in the end, it's all imagination that doesn't translet to any change in the quantity of Bitcoin you now have in your portfolio.
If you've known Bitcoin at the time it's at $500 and even had the resource to buy it, chances are that if you're skeptical at the present that you wouldn't have brought even in that past. The past have gone and whatever decision you didn't make at the time should not feel ones mind in place of planning for what lies ahead of us in the future.
Instead of talking about past possibility that's already gone, it's best to concentrate on the present in anticipation of the future potentials of Bitcoin and how well we can be positioned ahead for it. We've seen a remarkable change in Bitcoin price from last week down to this point and that's relatively a small span of time if you're considering investing for the long term. In the future, the likelihood of Bitcoin going above $500k is eminent and because of that, it's only best to use this period to DCA upwards to that point instead of lamenting on what's already in the past.
I agree with what you just said. Regret is just a feeling of sadness and disappointment, but we can channel that pain into building our Bitcoin portfolio. Whatever has happened in the past has been done, we can't change it, but we can change what may happen in the future if we take a good approach now. It is in our hands whether we will regret it later in the future or not.
As for me, I have zero regrets. The only thing I felt sad about was that I didn't know about Bitcoin earlier. If I had known about it, trust me my portfolio would be reading millions of dollars through mining and earning because I had a keen interest in technology at that time. Good thing i can afford to buy with my DCA now. What's more important now is the accumulation stage i am in. Later in the future we will all be happy and that feeling of regret will never be known to us again.