Some good answers here, and some interesting ones. But here’s (I think) a key perspective mostly missed:
In Christian thinking, life is good. Messed up, but good. Heaven is a vague term for where God is, and the End Game is us being alive again on Earth - either this earth, healed and fixed; or a completely new earth/world from scratch, depending on who you ask.
So even though we hope for something better, living now is good. And even though the real problem of death is solved, death is still bad per se.
That’s not quite the whole picture, and those who grow closest to Jesus are often both very glad to be alive - for loving/helping others even more than for themselves - and looking forward to “going to heaven” where they can be in the undiminished presence of God.
Paul in the Bible put it:
For me to live is Christ and to die is gain
I.e. to carry on living is to do Chris’s work; but to die is gain for me personally.
And which I prefer I do not know… I desire to depart and be with Christ, which is much better. But to stay on in the flesh is necessary for your sake.