People going short term, after ATH BTC/ETH what is safe $ to sell at?

[beamin]

I'm going short term well long but want to lock in profits. I have 0.1 BTC@$38,900.00 and ETH 0.8 @960.00$ = $4829.00 Jan 7 at 8:30EST.

I already made my profit by buying in at 17k and 32k so if this ATH is just going to reset when should I pull out my coins? When my wallet hits $4,500 (BTC=35k?) I realize it could go down to 30k then go back up to 40k a few days later, which I will buy back in with half the money.

My plan is sell and lock in profits and if it goes low or resets back to 15k I'll buy back in.

 But my question is when to set that stop limit order?