I drink energy drinks that contain caffeine.  Can you elucidate on the pros and cons of caffeine consumption?
Well caffeine is legal and unregulated almost everywhere, unlike other psychoactive substances, so that sure is a con.
i sometimes feel out of it when i drink too many, almost like an overdose.  Is there a limit on how much caffeine i should consume?
Definitely, caffeine is a psychoactive drug and should be consumed in limited quantity. The exact amount depends on the person though.
You are saying that caffeine is a drug like heroin?  I wish that i had known this years ago.  I am an addict.
Psychoactive drug
A psychoactive drug, psychopharmaceutical, or psychotropic drug is a chemical substance that changes brain function and results in alterations in perception, mood, consciousness, cognition, or behavior. These substances may be used medically; recreationally; to purposefully improve performance or alter one's consciousness; as entheogens; for ritual, spiritual, or shamanic purposes; or for research. Some categories of psychoactive drugs, which have therapeutic value, are prescribed by physicians and other healthcare practitioners. Examples include anesthetics, analgesics, anticonvulsant and antiparkinsonian
Caffeine
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is the world's most widely consumed psychoactive drug. Unlike many other psychoactive substances, it is legal and unregulated in nearly all parts of the world. There are several known mechanisms of action to explain the effects of caffeine. The most prominent is that it reversibly blocks the action of adenosine on its receptor and consequently prevents the onset of drowsiness induced by adenosine. Caffeine also stimulates certain portions of the autonomic nervous system.
Caffeine