Bhagavad Gita Verse 37, Chapter 18

yattadagre vishameva parinaamemritopapam |
tatsukham saattvikam proktamaatmabuddhiprasaadajam || 37 ||
 
That which is like poison initially, but is like nectar in its result, that joy is said to be saattvic, born of one’s mental purity.
 
yat : that
tat : which
agre : initially
visham : poison
eva : like
parinaame : in its result
amritopapam : like nectar
tat : that
sukham : joy
saattvikam : saattvic
proktam : is said
aatmabuddhiprasaadajam : born of one’s mental purity
 
Most of us dread going to the doctor’s office for a vaccination. Some of us will try to postpone, or even cancel, an upcoming vaccination. What causes such fear? It is just a little bit of a pinch, that too for a few seconds, caused by the needle of the syringe. Fear is also caused by the anticipation of this pain. But we all know that any vaccination is given to us for our own long term benefit. It will prevent us from catching all kinds of diseases that can cripple us or even kill us.
 
So therefore, the reward for bearing pain is extremely beneficial to us. Shri Krishna says that sattvic joy is similar, in that when we first begin to experience it, it is quite unpleasant, but in the end, it is as pleasant as nectar. No spiritual path is easy to take up in the beginning. In karma yoga, one has to work selflessly, chipping away at the ego. The leap of faith needed for bhakti is difficult for people who have grown up doubting everything. Jnyaana yoga requires a high degree of awareness, whereas most of us lead automated robotic lives where someone else has done out thinking for us.
 
All of these practices have their goal as the purification of the mind, and of removing its three main doshas or faults: mala or selfish desire, vikshepa or lack of focus, and avarana or ignorance. Unless these three faults are diminished to a great extent, we will be unable to comprehend the nature of sattvic joy. This is unlike any joy we know so far, because it does not depend on any external factors such as objects, people or situations. It comes from inside, from the intellect that has turned inward towards the self.