Meaning of the song "Nenje Ezhu" from Mariyan (Tamil Lyrics - Tamil Release)

This song from Mariyan has deeply touched me. The meaning is profound and I just cannot help myself listening to this song again and again. It is like a roller coster ride. If you have not yet listened to this song, do it right now. Here is an audio of this song. 

Pallavi

aayiram sooriyan suttaalum (Thousand Suns might explode at once)
karunaiyin varmam karainthalum ( Mercy may cease to exist)
vaan varai adharmam aandalum ( The evil might become very powerful)
manithan anbai maranthaalum ( A human may forget the emotion of love)
valiyaal un uyir theinthaalum ( Pain would eat you slowly)
un kaadhal azhiyaadhey ( But your love will never leave you)

nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
kaadhal endrum azhivathillai ( Your love will never vanish)

Charanam 1

iruvar vaanam ver endralum (We might be looking at different skies)
un nenjinil ninaivugal azhinthaalum (You may even forget our memories together)
paruvangal uruvam maarinaalum (The seasons may change their nature)
kuzhanthai sirikka maranthaalum (A child may forget how to smile)
iyarkaiyin vidhi thadam purandaalum (Nature may itself be altered)
un kaadhal azhiyaadhey ( But your love will never leave you)

nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
kaadhal endrum azhivathillai ( Your love will never vanish)

Charanam 2

anjaathey (Do not fear)
thunjaathey (Do not give up)
ini endrum illai vedhanai (You can make the pain go away)
puthithaai (Be born again)
pirapaai (Happyness)
vazhi engum un mun poo mazhai (Your love will live long)
anbaalum un kaadhal ithu vaazhum sathiyame (All this is a promise that will come true)
tholaiyaadhey (Never get lost)
entha irulilum maraiyaadhey (Do not lose yourself to the darkness)

nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
kaadhal endrum azhivathillai ( Your love will never vanish)

aayiram sooriyan suttaalum (Thousand Suns might explode at once)
karunaiyin varmam karainthalum ( Mercy may cease to exist)
valiyaal un uyir theinthaalum ( Pain would eat you slowly)
un kaadhal azhiyaadhey ( But your love will never leave you)

nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
nenje ezhu., nenje ezhu., (Arise Heart, Arise Heart)
kaadhal endrum azhivathillai ( Your love will never vanish)