What they said.
I'm mono. My partner is poly. I have decided not to "do Poly" for myself - I'm not "wired" that way, and really have no desire for more than one partner. However, I did choose to be in a Poly relationship ("sharing" my partner with others). The two ARE different (mono or poly self versus mono or poly relationship) and don't necessarily need to match. However, if they don't match, there's probably going to be a lot of work in front of all of you.
It's not impossible, though. Hang in there. Two years in, things seem to be smoothing out, such that my partner is dating someone else, she and I are meeting tomorrow, and I'm less nervous about it than she is.
One day at a time.
Mono. Divorced, two kids (DanceGirl, 14; and PokéGirl, 11), two cats, one house, many projects.
My partner. Poly. In relationships with me, Xena, and Noa.
Poly. In relationships with Chops and Noa, and dating others.
Married, Poly. In relationships with Chops and Xena (individually).
Blog thread: A Mono's Journey Into Poly-Land (or, "Aw hell, there's no road map?!")
Slightly more polished blog with a mono/poly focus: From Baltic to Boardwalk