Something like this was discussed by Kelly McGonigal in "The Willpower Instinct". A couple things that might help:

Avoidance - Complete avoidance is probably impossible, but you might try limiting your exposure to such things, particularly when you are vulnerable to making poor decisions. The old advice "don't go to the store when your hungry", might be related to low glucose levels (which affect decisionmaking).

Controlled exposure w/ reflection - I remember wanting toys when I was younger based on what was shown in commercials. After a couple disappointments, I got a little better resisting the ads. That said, I could probably use some recalibration...

All in all, mindfulness and an information diet. I've seen this particular field (ads, store layouts, etc) referred to as choice architecture, perhaps you could do some choice architecture of your own, to guard when your defenses are down. Essentially, develop good routines and make good choices ahead of time and stick to them.