If i was one of such people, i will think about it from time to time, but i would not make it a lifelong regret, i sold at a profit and back then it was something worthwhile,
Same here, but who wouldn't? As we are talking about millions and billions here or even more than that? But it is better to take action and invest even if we think we are late than have a lifelong regret as you said there. Another thing that won't give us a lifelong regret is if we are like you that already benefit somehow from the coin. Imagine if BTC didn't continue? That should make you feel more reliefed.
i know if you compare it with BTC's current value, then it is nothing, but who would have known.
Not totally nothing because back in time the price is only cheap but look at the price now. Buying it will only make us struggle a bit, and that makes us to earn lesser. It is a different story anymore if we hold for a very long time and refrain from buying again.