Playing big characters changes me by either exposing more of myself to view than I saw before or by introducing into my own characterological DNA news strands of personality I hadn't before possessed. I welcome the change, or the forced acknowledgement of self (or both) even when it's disturbing. I take a step out of solipsism when I do: e.g., once the show was over, I couldn't leave behind fast enough the abusive and guttural Mr. Klemper (a small role but major force) in The Boys Next Door, but channeling his violence and jealousy through my own body stepped me nonetheless closer to an enlarged experience of, and regard for, the human condition. Likewise with Malvolio, and Titus, and James Tyrone, Jr. (a little less so with Harold in Orphans and Henry in Henry IV I & II). It'd be nice to play a hero some day.
James Tyrone, Jr. is tough for me to like or entirely admit in but I'm aided by how acting technique both distances and brings him closer to me as I work both to recreate the essence of Eric's work and make Tyrone 'my own.' Distancing and collapsing-distance between self and character are mutually supporting modes, which allow me to pry open or build new doors within myself. I find the process challenging, but extraordinarily fun, and ultimately spiritual.
Taking in a big new character is like discovering that I'm The Hulk, an alarming, but enlarging discovery.