A favorable or hopeful aspect, as in Bob is inclined to look on the bright side of everything. This idiom uses bright in the sense of “lit up with gladness or hope.” [First half of 1800s] Also see glass is half full.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
Examples from the Web for bright side
Why not drop each of us off to take a quarter of the bright-side and work our way in?Gold in the Sky
Alan Edward Nourse