Here's a simple trick - stop shifting the blame on other people.

I really don't get your defeatist attitude:

1. You don't have the willpower to stop eating sugary stuff

2. You don't have the willpower to have a conversation with your spouse to stop buying sugary crap

3. Barring 1 or 2, you aren't talking to your kids to convince them to stop demanding less sugary stuff or aren't presenting them with tasty alternatives.

I'm sure in response to this I'll get a lot of angry replies to the tune of "it's not so simple" or "I don't have enough time for that" or "willpower theory is a myth".