The Bible is very clear about what "our part" really is:
"26For ye see your calling, brethren, how that not many wise men after the flesh, not many mighty, not many noble, are called: 27But God hath chosen the foolish things of the world to confound the wise; and God hath chosen the weak things of the world to confound the things which are mighty; 28And base things of the world, and things which are despised, hath God chosen, yea, and things which are not, to bring to nought things that are: 29That no flesh should glory in his presence." (1 Corinthians 1:26-29)
We have no part, because we could bring no part to bear in redeeming ourselves:
"1And you hath he quickened, who were dead in trespasses and sins; 2Wherein in time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience: 3Among whom also we all had our conversation in times past in the lusts of our flesh, fulfilling the desires of the flesh and of the mind; and were by nature the children of wrath, even as others. 4But God, who is rich in mercy, for his great love wherewith he loved us, 5Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;) 6And hath raised us up together, and made us sit together in heavenly places in Christ Jesus: 7That in the ages to come he might shew the exceeding riches of his grace in his kindness toward us through Christ Jesus. 8For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: 9Not of works, lest any man should boast. 10For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them." (Ephesians 2: 1-10)
Paul could not repeat it enough: By grace, you are saved. By His favor, not our fervor, are we taken from death to life. God our Father has seated us; we do not seat our selves. We are saved by what He did, not what we did or do, or will do. "Not by works", "gift of faith".
This is something that we all have a problem with as human beings, convinced that the world will not turn without us. Last time I check, God has the world taken care of:
"He stretcheth out the north over the empty place, and hangeth the earth upon nothing." (John 26: 7)
He does that, not us. He hangs the world on nothing, yet He holds us with both hands:
"28And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. 29My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand." (John 10: 28-29)
He has taken care of everything. Our job is to believe it.