Leaking at the Nose: The nose bridge is too wide or too narrow for your face. Try goggles with adjustable nose bridges or a different bridge size.
Leaking at the Outer Edges: The socket shape doesn't match your face. Try a different gasket profile, some are rounder, some more elongated.
Pressure Headaches: The goggles are too small, or you're over-tightening the strap to compensate for poor fit. Try a larger size or different brand.
Constant Fogging: Your eyelashes may be touching the lens, or the anti-fog coating may not suit your needs. Make sure there's clearance, and consider goggles with stronger anti-fog treatment.
Red Marks that Last Hours: The gasket is too firm for your skin or the size is wrong. Look for goggles with softer silicone gaskets or a larger socket size.
Shifting During Dives: The profile may be too high and catching water. Low-profile racing goggles sit closer to the face and resist displacement.