All religions seem to agree on a primal state of undifferentiated union, from which we have become tragically separated.
The mystical path seeks again that primal unity, by trying to discard that which differentiates, that which separates.
However, that is an end to the individual and to freedom. It is to regard this mortal life as wholly error, useless - it would be better not to have been.
The Christian yearning is instead for love. Love means that there is a joining that is not unification. Love means that individuals, from their individuality and freedom, join again with reality.
This is something most have experienced. For Christians, love is the highest state, the highest goal. That which is yearned for more than unity.
Heaven is a place of love, not unity.
Those who wish for Heaven, find the way by love of Jesus, not by becoming one with Jesus.