When was the last time you saw your wife? I'm not talking about her being visible. I mean see her with another man's eyes.
Do you remember when you loved the curve of her hips? You oogled her butt. You rubbed her thighs. You played in her hair. You sniffed her perfume. You held her and committed to memory how she smelled and how she felt. Do you remember when she wasn't yours? Just because you're used to her doesn't mean she's changed.
You need to see your wife, really see her like someone else would. That will keep you from taking advantage of her.