Dear Heart,
The Definition of Feeling, according to dictionary.reference.com, is the general state of consciousness considered independently of particular sensations, thoughts, etc.
In truth, the definition of feelings should be simple. However it's not. Many of us don't know what we are feeling, but more so we don't know why we are feeling certain ways. Sometimes the feelings we get, the "butterflies", are the same feeling as that of happiness and that of fear.
The most common feeling next to fear, is loneliness. But not necessarily that depressed loneliness but that loneliness of eternity. Even though you've accepted that you'll probably be alone forever, you still have a feeling of hope. But in reality that eternity of loneliness leaves diminishes whatever little thread of hope you had.
Sadly, you feel this way sporadically. But you don't have an inkling of what's to come. And that's what scares you more than an eternity of loneliness, but the fear of the unknown.
So maybe, the true definition of feelings is fear. I fear LOVE.
Sincerely,
The Mind