Most humans have a certain need for closeness. Likely you are either introverted or fairly isolated, you feel alone, so you feel much greater an urge to be close to someone. So what would be a simple attraction for someone else turns into love for you. Your mind subconsciously strives for that kind of attachment, it knows you need it, so it's going to get it at whatever cost, no matter the other person's feeling, your 'chances' and whatnot.
Basically, get some friends.
And then, after some time, either instantly, or slowly, but surely, you realise that that naive love you were feeling is not meant to be, which throws you even deeper into the isolationist trap you are stuck in, the cause of the whole issue.
A socially healthy person would learn from the experience, watch out for this kind of feeling, perhaps rationalise it a bit more to avoid the disappointment that could follow, reserving the stronger emotions for later. Not you, however, you are in desperate need for that close bond, so you will continue this cycle again and again, up until you give up on people completely, becoming an apathetic shell of a person.