Heaven is heaven because of the presence of God.
As the Psalmist says, we can find the fullness of joy and pleasure in His presence.
Psalm 16:11 - Thou wilt show me the path of life: in thy presence is fulness of joy; at thy right hand there are pleasures forevermore.
The Bible doesn't give a clear idea about all that we would do in Heaven. However, we know for sure that we would be with Jesus, serve/worship God and will be free from pain, tears and sins. Yet, for a terrible sinner like you and me, who deserves Hell, an entry into Heaven itself is a great gift. But, remember that our God is abundant in wisdom and loving-kindness. If the temporal world with all the curses of sin and evil is this beautiful and amazing, how much more awesome will heaven - God's dwelling place be?
Revelation 22:3 No longer will there be any curse. The throne of God and the Lamb will be in the city, and his servants will serve him.
Revelation 21:4 - And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.
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How to be sure of being saved or going to heaven after death?
Believe in the ONE True Triune God(Father, Spirit, Son) and that Christ came down to earth as a man, died on the cross and bought our pardon, and is risen on the third day. Accept Christ ALONE(not self-righteousness, not Mary, not Saints, not religion, not sacraments) as your personal Savior.
We are saved by GRACE, through FAITH, in CHRIST ALONE.
A disobedient believer will usually be chastened or disciplined by God in this life and lose rewards in heaven.
Jesus is the Only Way to Heaven
This Post: What will we do in heaven?
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Accountability of Believers-Judgement for Believers
The White Throne Judgement
Does God heal every sickness?
Why does God allow Suffering and Pain?
Who is Satan?
Does God answer all prayers?
Is "Jehovah Witnesses" a False Religion
Is Catholicsm a Cult?