A literal mire is a bog or a swamp. (And, mire can also be ooze, mud, or dirt.)
We'll focus on the figurative meanings.
A mire is any bad situation that's hard to get out of.
And, to be mired, or to be mired in something, or to be mired down, is to be stuck in a bad situation.
Part of speech:
Both a noun ("this mire," "such a mire," "those mires")
and a verb ("they're mired," "he's mired in a family drama," "we're mired down").
Other forms: mires, mired, miring, miry
How to use it:
To use the noun, talk about "the mire of something:" the mire of doubt, the mire of bureaucracy, the mire of economic stagnation. (If your meaning is clear, you can drop the "of:" "She's still wallowing in that mire.")
And to use the verb, talk about a person, a group, or a thing that's mired, often mired in something else: mired in chaos or turmoil, mired in conflict or war, mired in drama or controversy, mired in the long and complex process of obtaining the government's approval.
Finally, to use the adjective, "miry," talk about miry roads, streets, and ways; miry swamps and depths; miry ditches and grounds, etc.
Although keeping a journal is healthy, too much writing about the past can mire you in it.