That's the thing about platitudes--they are time-worn clichés for the most part.  Hence, they have virtually all been "written by someone else." 
Merriam-Webster defines it thusly:
plat·i·tude: noun
A statement that expresses an idea that is not new
1  the quality or state of being dull or insipid
2  a banal, trite, or stale remark
But--you want "original?"  Here's mine, when someone is doing something either questionable, or with which I don't necessarily agree, but agree that they are free to do as they choose:
"Whatever flips your switch."