Jesus knows what it means to be human
When my wife was battling cancer, I came to understand a lot about the disease and its treatment. I shared my wife's experiences in every way I could, yet one thing I never came to understand was what it is like to have cancer invade my body. Only those who contract this disease know what it means to have cancer.
We gain knowledge either objectively or experientially. Objective learning comes from observation and study; experience opens an entirely different understanding not possible by observation.
We understand that God knows everything, but does his knowledge extend into every experiential possibility? We are told that God can't be tempted (James 1:13), so how could he relate to our experience when we struggle against sin?
Likewise, God, being everlasting, did not know what it was like to die until he came to Earth in human form through Jesus Christ. When God took on flesh, he experienced in every way what it means to be human, except to sin.
This is the good news of Christmas. Jesus, by becoming human, knows what it means to be human. This makes him the perfect one to represent us to the Father (Hebrews 4:15). In doing so, he does not tell the Father a number of facts the Father already knows. He shares his knowledge of experience.
Because Jesus experienced being human, he can empathize with our situations and speak to the Father with complete understanding on our behalf.
Knowing this should help you to have a very merry Christmas.