Diversify or Increase Share in a Favored Company?

I have about 12 companies in my portfolio, but if course we all have our favorites. The reasons are many, but I’ve always heard that you should own companies that interest you, have relevance in your personal life, and that you feel good about owning. With that being said, I’m deciding whether or not to add to one of my companies or initiate some new holdings. For instance, would you bump up to 1000 shares of you had the opportunity from about 800, or do you continue to diversify?