Why are my emotions having input on my decisions? How can I eliminate them or suppress them for good?

You can't eliminate your emotions. We are emotional beings. When you suppress and bottle up your emotions, they will always resurface. And if you make a habit of suppressing them, often, they come back in the worst ways, at the worst times. What you need to do, instead, is learn to control your emotions. If you don't want them affecting your decisions or arguments, don't let them. But at the same time, let them out in other ways at other times. And we -all- have times when our emotions get the best of us. It's bound to happen. And when it does, don't think too much of it. Just move on. Beyond that, relationships are entirely about emotion. You can't logically plan a relationship. You can't decide when to fall in love. It just happens. You are completely subject to your emotions. There's nothing you can do about it. Just let it happen, and enjoy the ride.