Personality change following neutering

Apparently, my 15 month-old tom-cat Stinky has reverted to kittenhood
after castration. He plays with his sitster like he used to as a
kitten,
is much more fearful (of loud noises, people, etc), goes out much less
frequently and sleeps a lot more, and has stopped roaming at night.
The only good thing is that he no longer comes home with fighting
injuries. Still, it makes me feel very guilty.

Is Stinky's behavior change normal? Will he ever regain his confidence
and swagger?
Thanks.