Unrequited love is love that is not openly reciprocated or understood as such, even though reciprocation is usually deeply desired. The beloved may or may not be aware of the admirer's deep affections. The Merriam Webster Online Dictionary defines unrequited as "not reciprocated or returned in kind."

"Some say that one-sided love is better than none, but like half a loaf of bread, it is likely to grow hard and moldy sooner."
The inability of the unrequited lover to express and fulfill emotional needs may lead to feelings

Emotion

Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...

 such as depression

Depression (mood)

Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...

, low self-esteem

Self-esteem

Self-esteem is a term in psychology to reflect a person's overall evaluation or appraisal of his or her own worth. Self-esteem encompasses beliefs and emotions such as triumph, despair, pride and shame: some would distinguish how 'the self-concept is what we think about the self; self-esteem, the...

, anxiety

Anxiety

Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...

 and rapid mood swing

Mood swing

-Associated disorders:Mood swings are commonly associated with mood disorders including bipolar disorder and depression. In patients with cases of bipolar disorder, the patient experiences serious mood swings that last for days or even weeks...

s between depression and euphoria

Euphoria

Euphoria is an emotional and mental state defined as a sense of great elation and well being.Euphoria may also refer to:* Euphoria , a genus of scarab beetles* Euphoria, a genus name previously used for the longan and other trees...

.