Question about Position Sizing in DAX Futures

I'm trying to understand how to adjust position size to match my risk tolerance per trade. I mainly trade DAX futures and often find that the market is so volatile that my stop loss gets hit too frequently, even though my trade plan seems reasonable. Or sometimes, it goes against the idea of holding a position longer if I had reduced its size.

Normally, I use a fixed percentage risk per trade, but when volatility swings heavily like this, it feels like that percentage doesn't align with market movement. So, I'd like to ask fellow traders who trade DAX or European equities futures how they manage position size during high volatility. Does anyone use ATR for calculations, and how effective is it? Or are there other interesting methods?