Good for you if you sold yours at 19k or 18ish and tried to buy back now at 16k. Coz sometimes its much better to get even just 90% than +100% or hodling for long time and ends up in loss again.
You only lose when you sell, if you bought high and the price later decline, you continue holding. The growth of bitcoin isn't slowing down anytime soon. There are more innovation and adoption yet to come, buying bitcoin now irrespective of the price and holding, ignoring any current market movement is the best way to Invest.
If you're good at profit taking and rebuy then continue as there are many ways to reach a goals, everybody must not be a trader neither a holder. The corrections we're experiencing is a healthy one so it shouldn't lead to regret of not securing profit when the opportunity presented itself.