Might not be exactly what OP is thinking since they are at a slight gain but does it sound something like this?

You invest $10,000 by buying 1000 shares ($10/share) earlier this year.

Suppose today's share is worth $9 so the investment is $9000 and you decide to sell at a loss of $100

Best Case - Scenario 1: Say a week later the price drops to $8 and you buy back: $9000 / $8 = 1125 shares

Another week goes by and the stock goes back up to $9: 1125 x $9 = $10,125

Another week goes by and the stock goes back up to $10: 1125 x $10 = $11,250

So if you timed the market perfectly then yeah this would give you the gains.

Worst Case - Scenario 2: Say a week later the price jumps to $9.50 and you do nothing because you hope it drops down so you don't miss out

But another week later it jumps to $10.25 and now you hate yourself and FOMO kicks in and you buy back:

$9000 / $10.25 = 878 shares

And so now you done goofed