Piglet is only a very small little animal so therefore he tends to get very nervous and frightened. (So would I if I met a Heffalump!!)
I think Piglet is the most generous of all the animals in the forest, he is always willing to help a friend in need. For instance: When Owl's house burns down Piglet lets him have Trespasser's Will, (Piglet moves in with Pooh) which I think is a very noble thing to do. Especially if you're only a very
small little animal.