It happens Mark
I've had some right shitters when I've been off my game or not in the right frame of mind.
I guess the best tips I can give is, be aware of your shape, shine, silhouette and movement.
Consider how you smell - I wear a DPM smock that hasn't been washed for months.
Also, when stalking in, keep low (even at night) and roll your feet from heel to toe, along the outer edge of your foot.
When using NV with IR, I like to keep quarry on the outer edge of the screen until I'm ready to take the shot. That way I'm not pointing the red glow dir