To be kind-hearted is a beautiful way to live your life in the way that you're bringing so much positivity, although it's good to be aware of a few of the reasons why it can be bittersweet.
1. Others May Take Advantage
Being a kind-hearted person is a great thing to be, although one of the reason it's bittersweet is that others may take advantage of our kind nature. This is especially true when they seem to be constantly 'taking' what we naturally give and offer, and in most cases we won't receive anything from them in return. For this reason it becomes a one-way street where it should always be two-way.