Surah Dhariyat verse 56
"I have not created the jinn and men except for this that they should worship Me alone."
As such we strive to please God almighty. God gives us criterion of how to live in this life, to be grateful to him for all he has provided for us including our existence.
This life is nothing but a test for us and a temporary residence. As a result, for our sincere good deeds he will reward us and for our sins punish us in the after life.
What awaits us are things no eyes have seen, no ears have heard and no mind has conceived. The best we have to imagine what this will be like are similitudes to this world but magnified to unimaginable degrees. That will be the reward in the next life, an eternal life. A life of living similar to this but better, without suffering, without corruption, without prejudice, without jealousy, without any evil.
A person who suffered all their life in this world when shown for a second heaven will be asked if he ever suffered will say verily I have not. After having a taste of heaven for a mere second.
A person who boasted of pleasures in this life but denied God and did evil, debauchery and vain desires... when he will be given a second of hell, he will be asked has he enjoyed this temporary life the dunya, he will say verily I have not, I had no pleasure.
God calls this life just a game/entertainment and a past time:
And this worldly life is not but diversion and amusement. And indeed, the home of the Hereafter - that is the [eternal] life, if only they knew. Verse (29:64)