Setting Priorities

I am the non-ADD spouse, I have heard many say on this site that the best approach in dealing with issues, especially those which cause anger and frustration, is to set priorities and deal with one issue at a time.  That makes such sense, intuitively.  But I find myself having a hard time picking the one (or two) issues that matter most.  One, because there seem to be so many of them.  Two, because any issue taken by itself doesn't feel like it is "high priority" - rather, it's the cumulative effect over time that might make something a high priority.  And third, because whatever is frustrating me NOW is what seems to have the highest priority.  Also, I find that when my wife and I do address an issue, she sometimes can be pretty good about it for a couple of days (or even weeks), and then when I least expect it, she slides back into old behaviors.

So - do people recommend I set priorities based on how often behaviors occur, how frustrating they are, how "easy" they might be to change, or some other criteria?  Do I select MY top priority issue or is that something I work on with my wife?  If with my wife, how do we go about laying out and prioritizing the issues, without her becoming overwhelmed or feeling like a "bad" person because there are likely to be a lot of issues on that list?  Once I (or my wife and I) select a priority issue, how long do we focus on that issue before moving on to the next issue?

I would love to also have my wife lay out and prioritize her issues about what behaviors of MINE she would like me to address.  But whenever i try to get her to express what I do or don't do she has a very hard time coming up with anything.  (That says more about HER than me, as I definitely know I have lots of behaviors I can improve on - it's just hard for me to get my wife to acknowledge them.)