Doubt on definition of emotion I am currently reading Psychology and Life by Richard J. Gerig, where emotions are defined as


  A complex pattern of changes, including physiological arousal,
  feelings, cognitive processes, and behavioral reactions, made in
  response to a situation perceived to be personally significant.


I am not able to understand why anything other than feelings should be part of emotion. Isn't physiologica arousal, behavioral reactions and cognitive processes side effects of emotions rather than being part of emotion itself? For e.g. when you feel angry your heart rate increases. Why including factors (other than feeling) in definition make sense? I think this is also related to unlearning what has been already wrongly learnt where I am treating emotion just as feeling but nothing more.
You are asking some very important questions. And your skepticism is a sign of a scholar in my book. ;o) 

I agree with you that the definition provided by your textbook falls short.  

Emotion is a huge topic. It might help to narrow the scope of your question. 

I also suggest carefully defining a word like "feelings". For example, how are feelings and emotion different? (if they are).

Here is an article that will give you an introduction to contemporary research on emotion:

Critchley, Hugo D. and Sarah N. Garfinkel. "Interoception and emotion." Current Opinion in Psychology 17 (2017): 7–14. [Open access]


  Abstract: Influential theories suggest emotional feeling states arise from physiological changes from within the body. 
  
  Interoception describes the afferent signalling, central processing,
  and neural and mental representation of internal bodily signals.
  Recent progress is made in conceptualizing interoception and its
  neural underpinnings. These developments are supported by empirical
  data concerning interoceptive mechanisms and their contribution to
  emotion. 
  
  Fresh insights include description of short-term interoceptive effects
  on neural and mental processes (including fear-specific cardiac
  effects), the recognition of dissociable psychological dimensions of
  interoception, and models of interoceptive predictive coding that
  explain emotions and selfhood (reinforced by structural anatomical
  models and brain and experimental findings). 
  
  This growing grasp of interoception is enriching our understanding of
  emotion and its disorders.


Wikipedia has a good article on interoception.