What pisses me off most about science
 

Is that I've come to realize that none of our actions have deeper meaning beside being the most logical decision at a certain time and place. For instance, there is no such thing as a purely selfless act. Everything we do is in our own interest, for our own survival and/or complacency. You could boil it down to semantics or definitives, but words like 'altruism' have no basis in reality.

And don't forget, your desire to find goodness and meaning is itself a product of evolution designed to cause you to act in a way that perpetuates the species and is therefore purely pragmatic and without goodness or meaning itself. Embrace the nihilism.

I've accepted it, give me 10 years and hopefully I'll have embraced it

I wouldn't count on it. The best you can hope for, unless you're Tore, is a slow decline into apathy and a growing disinterest in the affairs of humanity. On the plus side Lord of the Rings will only get better and better.

This is HIGHLY debated.
Think of the example of tipping on a business trip to a new city.
You have never been there before. You visit a restaurant, alone. You're done with your meal, the waitress leaves you the check, and you leave her a tip as you walk out the door.
Why would you possibly do that? It in no way benefits you, you don't need to go through a socially awkward situation since the waitress is not in eyesight when you leave, and you will almost certainly never see her or anyone in that restaurant again.
Some studies have shown humans capable of truly altruistic acts.

That it does, fiction is the only place where things make sense to me anymore

You're left with a feeling of complacency about yourself, that you did the right thing.

If tipping the waitress made you feel terrible about yourself, you wouldn't repeat the process the next time.

I think what you're saying is true in some ways but it doesn't diminish altruism for me. If people do nice things because it makes them feel good, I don't see that as a negative. And I'm not sure how any of this connects to science specifically.

Because if you didn't then you would know that you hadn't and it would cause you to feel "bad". Or more accurately it would cause a release of chemicals or some such (yeah, accurate) into your brain that you would find unpleasant. This has been programmed into you so that you would respect cultural conventions and make you and the rest of humankind better able to interact with each other for the purpose of survival. And on and on until the entire concept of altruism just becomes a carrot and stick.

Science explains what is responsible for the actions, the thought process that goes into decision-making. And the impartiality of it all.