since it doesn't matter if you bought at $20k or at $5k as BTC will be worth millions eventually.
But you're only making assumptions, it's not something that you can guarantee with 100% certainty, bitcoin started increase a lot, we got to $10,000 and all news channels were euphoric and very optimistic and posted forecasts every time: "analysts predicting that by 2019 the price will be $40,000". even John McAfee made absurd predictions. the price reaches $12,000 and news channels remain euphoric and posting very optimistic forecasts and the cycle repeats up to $19,000. people sell their altcoins to buy bitcoin and used their credit/debit cards to buy bitcoin... so the price drops and many people enter in panic and sell their bitcoins... that's because people think: "if in a few months, the price went up from $1000 to $19000 - because it can not fall from $ 19000 to $1000? " so they sell!
What I want to say is that it is quite normal for people to sell in panic because nobody can guarantee with 100% certainty that the price will go up
I have no doubts personally that we are going to go for newer heights, eventually 6 figures a coin, there's literally no doubt in my mind, because I understand the implications of what bitcoin is as a store of value, and what bitcoin can become with second layer scaling.
It would require a total disaster for bitcoin to fail, but outside of that, we will keep going up long term while surviving the obligatory bubble and burst cycles that anyone that has been in bitcoin for a while is comfortable with.
Of course, nothing is guaranteed in finance, but nothing is guaranteed in life, in the sense of you can die tomorrow in some stupid accident. But if all things go as they should, we'll see 6 figures per coin within the next decade, probably way earlier than most can fathom.