Fighting the Overfitting Beast: What's your secret?

Been diving deep into the strategy review section lately, and the overfitting discussions are hitting home. It feels like every time I think I've found a solid edge, I go back and test it on slightly different data and it just crumbles. Anyone else struggling with this? What are your go-to methods for validating a strategy without letting it become too specific to past data? Curious to hear real-world approaches from the Tradeverse community.