Gita 04.31 explained
nāyaṁ loko ’sty ayajñasya
kuto ’nyaḥ kuru-sattama
Word for word:
O best of the Kuru dynasty, without sacriﬁce one can never live happily on this planet or in this life: what then of the next?
Verse fragment here (only 2 lines c &d part of the verse are here other two parts were clubbed with previous verses 4.29 & 4.30)
nāyaṁ loko -> not in this world. Asti . ayajñasya -> Without performance of Yajna. => Without performance of Yajna even in this world, loka people will not be happy. kutaḥ — where is; anyaḥ — the other; kuru–sat–tama — O best amongst the Kurus. This reference is to Arjuna that you are not the kind of person who will not do Yajna, you will definitely do Yajna, but for those who do not do so, what to tell about next world even in this world also they will not be happy.
If people will not do sacrifice people will not be happy even in this world also. Generally people go out to do enjoyment when they are self-pleasure centered. Me first and me alone. All of us are “I” specialist. People will not get any satisfaction, they may get some titillation. Some people lay down their life for nation, so at one level we can think that this person is at illusion why he is thinking that I am the body, and my country, this may be illusion from spiritual perspective but within the realm of material this is nobler than those who are living just for themselves trying to seek their own pleasure. When one lives by this principle he will be become purified up to certain level and one gets fulfillment, as he is living for others.
Those people with only enjoying mentality, their hearts are empty, their hearts are filled with fears and mind filled with desires they are on the verge of tears and they say cheers.
…Fear – what will happen … what will go wrong… am I looking attractive… mind filled with desires – I want that, I want that, that person got a better dress than mine… that person got better car … his spouse is better…because of this they are on verge of tear … this is just showcasing…they just put a big smile in front of others but their heart is empty … they talk about love but love has no meaning without sacrifice. And highest level of sacrifice is Love for Krishna.
So Krishna is saying even in this world also people cannot be happy without sacrifice. Same principle applies at religious and spiritual level also. Higher is the cause for one’s sacrifice, greater is the happiness and fulfillment one experiences.
So meaning of sacrifice is to give up something little for something great. The greatest is the eternal relationship with Krishna and it is ever-increasing fulfillment, so we should give up flickering pleasure of this material world, Krishna says at some level everyone has to do sacrifice otherwise even in this world person is not happy what to think of next world.