To lead a peaceful life,one must follow the sastras which are the rules of the almighty that cannot be changed by passage of time(i.e.kruta,thretha,dwapara&kali yuga).The almighty says,
“Shruthi smrithi mamaivaagya yaasthaam ullangya varthathe|
Aagya chhedi mamadhrrohi math bhaktopi na vaishnavahah||”
Which means,vedas and sastras are my commands and one who surpasses these rules have breaken my laws and cannot be considered as my bhakta or a vaishnava.
So everybody who seek the grace of lord must follow the smrithis(dharma sastras) in order to get rid of sins and to attain purity of mind.
It is said that so many sastras which binds every humanbeing in this world is meant for purifying the mind(chitta shuddhi).Aadi shankara in his viveka-choodamani says,
“ CHITTA SUDDHAYE KARMA NA TU VASTHU UPALABDAYE|
VASHTHU SIDDHIRVICHARAENA NA KINCHITH KARMAKOTIBIHI:||”
Which means, rituals are meant only to purify the mind and not attain almighty but he can be known only through vichara(introspection) ¬ by doing a crore of rituals.
Even if a person attains the knowledge of the almighty’s by his grace he should perform karma(rituals) for the sake of loka sangharah:(welfare of the world). Lord krishna in shri bhagavath geeta says,
“yath yath aacharathi shrestahah thath thataeva etharo janahah:|
Saha yath pramanam kuruthae lokahah thath anuvarthathe||”
i.e.the general public is used to follow whatever the elite(jnani= self-realised) does.for e.g. if he doesn’t perform karma ,others stop doing karma.
So,in order to safeguard the world Lord Krishna orders the elite to be an ideal for other people by doing karma.
It is said in mahabhashyam that
“Brahmanaena nishkarano dharmahah shadango vedhadhyeyo gayyashcha” –(patanjala mahabhashyam)
Which means without asking reasons &questioning a brahmin must study the vedas with its six angas(parts) and follow the dharma sastras.
we should follow the sastras without asking reasons