Perhaps there is no greater question than this.
All religions it seems, are really concerned with this question!
How can a mortal man, unite with an infinite immortal God?
The basic assumption is that God desires sacrifice!
The ancients were great at sacrifice!
More modern religions focus on other forms of sacrifice, such as prayer, penitence, charity etc. etc.
The basic assumption is that God has an ego, hence if you sacrifice, he is fed.
The truth is, nothing can be farther from the truth!!!
As our sages teach us, that even if you do all the Mitzvos in the world, or all the sins in the world, you haven’t touched God at all!
In fact, nothing, even the Mitzvos in the Torah are anything, without a single bridge that enables humans and God to communicate.
The bridge is, that God must desire the sacrifice!
For example, what can a child give his parent? especially if the parent has everything he needs; if this is the case, the child can make the parent happy, if the parent chooses that the child can make him or her happy.
Ultimately, all that mitzvos and prayer etc. etc. boils down to, is not an intrinsic power that these things have, rather in the choice that God imbued them with, to transcend the boundaries of the finite and allow them to pump into the person who does them, the infinite.