What kinds of responses or feelings do you get in you that help you see there are boundary issues in you that need to be addressed?
I try to watch out for selftalk that involves me feeling obligated, resentful or impatient. (to name a few)
I rework those issues/feelings in my head is by asking myself what I really want, how it will play out; and then I check on my motivation and/or expectations.
Of course there's always the issue of whether by my actions I may be taking on someone else's responsibility or somehow am dealing with their consequences as if they belong to me.
I've found that sometimes I could consider the same situation and either take it or leave depending upon how I work all of those things out in my mind.
For instance...I used to work extra hours for reasons that were not in my best interest- but some of the time when I did go the extra mile I feel it was warranted- and not a codependent related thing.
I found that for me- it wasn't or isn't usually about a particular action in itself but more about what goes on inside of my head & heart that is connected to it.