Jacob was simply a perpetually happy person, and he carried this happiness with him like an aura, sharing it with whoever was near him. Lika an earthbound sun, whenever someone was within his gravitational pull, Jacob warmed them. It was natural, a part of who he was.
When a performance isn't working, it's usually because the actor is trying to do something and they're not able to express their idea very well. It's a muddled expression.