You Ask: Fearful Papillon Puppy

The fearful, or shy Papillon puppy can be born in a litter, where all other litter mates may have wonderful, outgoing temperaments.He can be noticed right away in early development stage. He will react in fear in just about everything:  rough playing litter mates, barks, loud noises, strange people,- you name it.
The puppy had the same experience, and treatment like all the others, but most likely the shyness will remain for the rest of his life.

So, rather overcoming the impossible, mold your life a little around his temperament.
A shy Papillon puppy does best in a quiet home with mature people, no children, and a regulated schedule.
If you picked up such a puppy from somewhere, have the house full of kids, constantly folks running in and out of the house, taking trips..... find a stable life-style for him somewhere else, where one is mostly home, has little guests and lives a quiet life. And get yourself a new puppy, from a reputable breeder, and look at the parents of the Papillon puppy.

If you do not deal with the shy and fearful puppy, he may  become a "fear-biter", but
under the proper circumstances a shy Papi turns out to be a devoted, sweet little guy.