As nobody's a crystal ball to perfectly predict price moves, I literally always ended up purchasing above the prices I had an opportunity to buy at. Therefore, I've recently simply went for "purchasing when the price drops" no matter by how much or what criteria it is.

The only criteria I might sometimes follow is if the price drops low enough for my average purchase price to move down too. However, that doesn't happen often at all so yeah, these are "gems" you could profit off. But at the same time, if Bitcoin drops right now to $3k again, I doubt you will be convinced it's a good idea to purchase. You never know how low it goes.

If you can get past the emotions and only take actions based on your gut feeling, I think you have much higher chances to succeed.