Bhagavad Gita Verse 23, Chapter 16

yaha shaastravidhimutsrijya vartate kaamakaarataha |
na sa siddhimavaapnoti na sukham na paraam gatim || 23 ||
 
He who dismisses the laws of scripture and conducts himself according to impulses of desire, he neither attains success, nor happiness, nor the supreme goal.
 
yaha : he who
shaastravidhim : laws of scripture
utsrijya : dismisses
vartate : conducts
kaamakaarataha : impulse of desire
na : not
saha : he
siddhim : success
avaapnoti : attain
na : not
sukham : happiness
na : not
paraam : supreme
gatim : goal
 
Imagine that we have to assemble a complex piece of furniture. Most people will follow the instructions given in the manual that comes in the box. But, for some reason, lets say we ignore the manual and build what we want based on a whim. What will be the outcome? We will be unsuccessful in building a functional piece of furniture. Consequently, we will not be happy with this outcome. Without following the manual, we neither gain success nor attain happiness.
 
Shri Krishna says that if we live our lives based solely on our desires, we will neither attain success in any worldly endeavour, nor will we attain worldly happiness. The supreme goal of self realization then is totally out of the question. Unfortunately, whenever we feel disillusioned, we usually seek guidance from the latest self help book, or try to emulate the lives of those who have had significant material prosperity. Such guidance may get us temporary happiness in a small part of our life, but will never solve our predicament holistically.
 
So then, what is the solution? Shri Krishna points us to the Vedas, the scriptures, as a guide towards checking our selfish desire-oriented life. He is in no way advocating a dogmatic, ideological or blind faith oriented lifestyle that imposes restrictions upon society. The Gita, in fact, presents the very principles of the Vedas in a format that is meant for practical individuals. The notion of svadharma, of following a career path that is in line with our interests and our qualifications, is a perfect example of guidance from the scriptures.