^Thanks. Giving the Tritium example made me understand it better.. :)
I also searched on the Tritium case and found out that after an electron is ejected, a small difference in energy with both sides of the equation (see website) exists. I can't really explain in that well but the website kinda does a great job explaining. Here's the quote I'm saying:
As you said, the proton has slightly less mass than the neutron. The mass of the electron makes up for this somewhat, but if you do the math, you'll see that there's still some mass "missing" from the right side of the reaction. Energy takes up the slack: the electron comes out moving very fast, i.e., with lots of kinetic energy.
In other reactions, the "leftover" energy sometimes manifests itself in different ways. For example, the nucleus that comes out is sometimes in an excited state--the remaining protons and neutrons have more energy than usual. The atom eventually gets rid of this extra energy by giving off a gamma ray.
So, I kinda "get" where ALMOST ALWAYS came from. It's because the "excess" energy can be given to the ejecting particle, accelerating it, making the particle eject faster, OR the excess energy can be given off as a GAMMA RADIATION. So, there's really two possibilities, but GAMMA RADIATION happens more often.
Thanks for the help! :)
http://www.colorado.edu/physics/2000/isotopes/radioactive_decay.html
http://www.colorado.edu/physics/2000/isotopes/mass_conservation.html