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one of the best strategies is to have enough backup money to keep buying at lower levels and it allows you to trade freely.

Not a sound strategy at all.
And what is 'enough backup money' - does it mean trading only 10% of your available funds on any one trade? Is it 1%? Or is it 0.1%?

Imagine having $1. You decide to trade 1c so you ensure you have ability to 'trade freely'. You make a good trade and double your money - that 1c is now 2c and your overall money is $1.01. Is this trading freely - maybe. But it definitely is trading boring. No human has that level of patience - eventually they will trade all their funds hoping for a 5 or 10% return and bam, market turns and everything is lost.
Theory is one thing - but reality is very different.

Why coming '2021'?
What is specifically important about 2021, or do you mean the future generally?

After 2020 supply of Bitcoin those generated by mining get half

So there will be great hype of Bitcoin in 2021

It will be very much similar to 2017

Oh gotcha - that makes sense now .
Thanks 😄