Believing or showing the belief that people are motivated chiefly by base or selfish concerns; skeptical of the motives of others.

I'd characterize my view as understanding that people may be motivated by selfish concerns, but not assuming that any given person I'm interacting with is. As far as "skeptical" in this context, I'd say it's a little too strong to describe my process/viewpoint. In the purest, binary form of "skeptical" vs. "unquestioning", sure, skeptical. But in the sense of "eying suspiciously", not so much.

"Extend[ing] the benefit of the doubt" and "keeping myself open to the possibility (and hope) that someone is being honest with me", for me, both describe what I'll try to describe more deeply:

Barring prior contrary experience with or knowledge of a person, I begin with the assumption that they are honest and not intend to take advantage of me. Any simple statements or requests they make that don't seem costly or detrimental to anyone, I'll generally accept at face value. If they present a statement contrasting with my current understanding, or if they request something of me that could potentially cause myself or someone else harm (bodily, reputation, resources, whatever), I start more consciously evaluating what they say/do to ensure as best as I can that I'm not being convinced of something out of line with my interests. I still don't assume here that their motives are malign, just that they may have too different of a worldview for me to risk not carefully considering what is presented to me.

In the event that I have or gain reason to think the person's interests may be against my own, I stay on much higher alert to avoid being conned or convinced of anything. Generally I'll also try to increase the physical and/or social distance between us, because my natural state is not suspicious and it's exhausting to keep that much guard up.