Jesus cried and prayed to God the Father who was able to save him from death (Hebrews 5:7), that the cup of God’s wrath on him be passed over (Luke 22:42), but God willed for him to be the passover Lamb that takes away and the sin of the world (Isaiah 53:10; John 1:29) and Jesus knew this. He himself had said earlier, that he had come to give his life (to die) as a ransom for many (Mark 10:45). Then why would Jesus pray and request that God save him from death?

We must be careful to recognize that when Jesus prayed for being saved from death, he prayed for being saved from the midst of death, and not necessarily to be spared from dying. In other words, Jesus prayed that from the midst of death, God save him, by resurrecting him from the dead and God heard (answered) this prayer of Jesus as we see from the account of the Resurrection, recorded in the Scripture (Matthew 28:6).

Points to ponder:
The Scripture affirms that we are all appointed once to die (Hebrews 9:27), but we are not appointed unto death (spiritual/second death) and all who believe in Jesus Christ, whom God heard and saved from the midst of death, resurrecting him, will also be resurrected from being dead in sin, to being dead to sin and to walking in the newness of life (Romans 6:4). If you were to die today, would you be dead?

Hebrews 5:7 (KJV)
7 Who in the days of his flesh, when he had offered up prayers and supplications with strong crying and tears unto him that was able to save him from death, and was heard in that he feared;

Romans 6:3-11 (KJV)
3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?
4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
6 Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.
7 For he that is dead is freed from sin.
8 Now if we be dead with Christ, we believe that we shall also live with him:
9 Knowing that Christ being raised from the dead dieth no more; death hath no more dominion over him.
10 For in that he died, he died unto sin once: but in that he liveth, he liveth unto God.
11 Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord.