For a series of three or more items to be a parallel, they must act as a single unified sentence be the same part of speech come before the verb in the sentence use different endings in each word

be the same part of speech

Explanation:

Parallelism consists in using words, phrases or clauses with an identical grammatical form. Therefore, for a series of three or more items to be a parallel structure, they must be the same part of speech.

e.g. "My favorite camping activities are fishing, hiking, and swimming."

This sentence uses three gerunds fishing, hiking, and swimming as predicative nouns.  This is correct parallel structure.  

pre-writing

why we feel good, or better, when we laugh?

is there a scientific explanation for this to happen?

which are the sources?

rough draft

laughter has a way of instantly connecting people and is one of the most basic and fundamental ways in which we communicate as human beings.

newport academy: endorphins reduce stress and strength social connections.

they combat anxiety and depression.

final draft

we know that when we laugh we feel better; when something is making us laugh it means we thought it was funny at some point, even if it was not meant that way. what we know is that it made us feel good. that is something we all can realize easily, but is it a chemical explanation for it to happen? of course there

according to joe bluett, laughter has a way of instantly connecting people and is one of the most basic and fundamental ways in which we communicate as human beings. also, he says that laughter can increase confidence, self-esteem, creativity, positivity and resilience, bringing positive changes to all aspects of our lives.

the newport academy says that, when we laugh, we release endorphins and that makes our body feel instantly relieved from tension and worry. endorphins also reduce stress and strength social connections.

therefor, laughter is the best to combat anxiety and depression.