My rookie tip: If you ever sell, don't sell it all, keep at least 10% of your corn for hodling.
I am thinking about a formula that aim to NOT sell more than 10% for every range - such as every 100% (or maybe less selling and a greater range?)
But it would go something like this:
Let's say that you started buying BTC at or near the top of the last bubble, but you stuck with it and you kept dollar cost averaging in. Accordingly, you have a average cost per BTC that is around $8k per BTC, and so you are a bit concerned about what to do.
You decide that you will sell no more than 10% of your stash for every time that the BTC price doubles (if it does)
Therefore, you have authorized yourself to sell 10% of your stash at any point of your own choosing at each point within the below prices ranges:
1) $10k to $20k (10% of total stash)
2) $20k to $40k (10% of total stash)
3) $40k to $80k (10% of total stash)
4) $80k to $160k (10% of total stash)
5) $160k to $320k (10% of total stash)
6) $320k to $640k (10% of total stash)
7) $640k to $1.2m (10% of total stash)

Etc. etc. etc
Reasonable? Maybe? Maybe not, but I know that no matter at what BTC price range that I am within, I am hanging onto most (90%) of my BTC within that BTC price range, and I can plug those numbers into a spreadsheet to project the size of my BTC stash and to consider whether I believe that those sales amounts would be reasonable for my own particular situation.
I can project, based on the speculation of my particulars, what will be the amount of BTC that I sell at each price point, what my BTC amount remaining after each of those projected sales points, how much fiat will I have raked in from each of the sales points, how such raking in of fiat adds up at each of the sales points (and cumulatively), and am I comfortable with those numbers?
If I am comfortable with the numbers, then I execute my BTC sales in accordance with the plan
If I am not comfortable then I tweak some (or all) of the variables of the plan... and reassess them until I am as comfortable as I can be with such plan in order to feel executing such plan when the BTC price reaches my range (or a specific price that I have chosen within the price range).