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."