RE: Negative emotions.
It is quite possible to live life without ever feeling negative emotions. It is a choice, and it is not an entirely difficult path to follow once one realizes that the choice of how to feel is indeed there.
I would think that a generally balanced personal nature and a cohesive world view may be a requisite, but having had some dealings with emotional disaster, (as we all have), I have found that one can remain honest and compassionate and aware, while at the same time regulating the amount of 'Bad' one feels.
When you feel that very palpable gnaw of rage, jealousy or envy creeping up on you, know that you can simply decide not to let that stuff in. My personal opinion is that negative emotions, while enjoyable in a bitter-sweet sort of way, are destructive, unhealthy and ultimately useless. I do not believe the Star Trek, Ship's Councilor types when they insist that sadness be worked through. It seems that the western fanaticism for both Heaven/Hell-based religions as well as Cult of Science Atheist and Gnostic belief structures are really, really bad for both people and the world.
Completely Unverified Personal Opnion #1:A number of world cultures still believe in a multiple-life, Karma based structure of reality. --And those cultures spent thousands of years existing as efficient, advanced societies operating under these structures, and they did so without toxifying the entire planet the way the cult-virus of Heaven/Hell/Atheist based industrial society has managed to do in less than two centuries. The attitude of, "I only get one shot at life! Who the hell cares what damage I leave behind in my mad dash to ‘live life to the fullest'!" can only propagate under such systems.
Completely Unverified Personal Opinion #2: Based on what I have learned from my own explorations into these matters, I strongly suspect that the soul who was your father has made the transition, learned a bunch of lessons from his life, and has many new adventures ahead. Don't regret or sorrow, or even bother praying to him, or whatever. Chances are you'll run into him again sometime when you make your own future travels.
--I recognize that these sorts of opinions are a long, long way from keeping with the general mind-set of such a heavily tech-oriented environment as this one, but then I tend to think that most of the western world has been hoodwinked into 10 hour per day slavery for the forces of greed and destruction, etc. Most people are very, very asleep.
So, don't worry. Your Dad is most likely just fine. Wish him luck and get on with your own lessons in life.
In any case, even if I'm wrong, (and I obviously don't think I am), you can't hurt yourself with these kinds of thoughts.
Remember: Multiple Life Theory is not a religion or a cult. --That is, nobody is going to pass the collection plate or try to save your soul, (nobody wins brownie points for bullying people into 'converting'). In fact, by most accounts, you accumulate bad Karma for doing stuff like that.
In the end Free Choice is the only thing that matters, so believe what you want.
It's entirely up to you.