H4C, go to
www.flylady.com. It's fun and inspiring and will help you get on track with habits. Putting stuff back or picking up is less about the mind than about habits.
Sadtonight, Oh, boy! I could regale you with stories, and I bet my ex trumps your H for messiness. Currently, there's a toilette that's been sitting by his kitchen door for almost a year. I still have some of his mess in my basement. It was terrible. I had his inventory of old books and paintings in my dining room, filling the basement, in my upstairs office/sitting room, filling a shed and filling the broken down subaru in the driveway. It caused me to much stress that as I vacuumed around the stuff, I'd just feel "I hate you, I hate you, I hate you." He would promise to clean up, but never did, and that made it worse.
Now, my ex wasn't at all concerned about my feelings on any front, and he did a LOT of other LBs. But Annoying Behaviors are lovebusters too. And being disorganized and messy is an annoying behavior.
So, you need to sit down when you aren't upset and talk calmly to your husband about how stressful you find it when stuff isn't put away. Share with him that it's so stressful that it hurts your marriage, and ask for his help. What would it take for him to be enthusiastic about putting stuff away? Can you give him some of his own "clutter" space? (If you do this, mark it off with tape. I kid you not.)
IF that doesn't work, you may want to try throwing the stuff away. "Oh, honey, I thought it must be trash since you left it out by the garage." Also, don't help him look for stuff that he can't find because he didnt' put it away.