The Christian has the advantage here because we can find actual answers to these questions. The atheist, the naturalist, they can't provide any real advice that doesn't boil down to picking yourself up by your own bootstraps. To them there is no meaning in life and so there can be no meaning in our lives. The Bible tells us a different story.
God doesn't expect success from us, we are never commanded to engineer victory or to be the best we can be at whatever we do; we only have to be obedient and entrust the outcome to Him. You see in God's economy none of the stuff around us matters in and of itself. My job is not there to bump up my pride, my skills and abilities are not to be used primarily for myself, my opportunities are not solely to provide for my needs and desires. We are called to holiness because only that will last.
"Therefore gird up the loins of your mind, be sober, and rest your hope fully upon the grace that is to be brought to you at the revelation of Jesus Christ; as obedient children, not conforming yourselves to the former lusts, as in your ignorance; but as He who called you is holy, you also be holy in all your conduct, because it is written, "Be holy, for I am holy."
(1 Peter 1:13-16)
Of course we should do our best and not slack, of course we should work hard as the things given into our care are a responsibility and a stewardship, but we are not defined by those things and if we never get promoted or if we lose our job entirely it is not the end of the world! Our job, our real job, is to seek to grow ever closer to our God and King. Everything else is a means to that end. Frustrating co-workers can make you more patient, an unqualified boss can teach you obedience and respect for position, never moving into more prominent positions can teach you contentedness and reliance on God, people who fail you can teach you forgiveness, persecution can root truth in our hearts, and being alone can draw you closer to God.
This life is a factory floor, where the raw material of our souls is machined and processed into the very people of God. When we mistake the process for the purpose we lose sight of the end product. "But how can we live when we don't depend on our jobs, relationships, etc?" I hear you ask. It's true that we can't pay the rent or make a car payment with holiness but that job and that paycheck were never what held you up to begin with.
"No one can serve two masters; for either he will hate the one and love the other, or else he will be loyal to the one and despise the other. You cannot serve God and mammon. "Therefore I say to you, do not worry about your life, what you will eat or what you will drink; nor about your body, what you will put on. Is not life more than food and the body more than clothing? "Look at the birds of the air, for they neither sow nor reap nor gather into barns; yet your heavenly Father feeds them. Are you not of more value than they? "Which of you by worrying can add one cubit to his stature? "So why do you worry about clothing? Consider the lilies of the field, how they grow: they neither toil nor spin; "and yet I say to you that even Solomon in all his glory was not arrayed like one of these. "Now if God so clothes the grass of the field, which today is, and tomorrow is thrown into the oven, will He not much more clothe you, O you of little faith? "Therefore do not worry, saying, 'What shall we eat?' or 'What shall we drink?' or 'What shall we wear?' "For after all these things the Gentiles seek. For your heavenly Father knows that you need all these things. "But seek first the kingdom of God and His righteousness, and all these things shall be added to you. "Therefore do not worry about tomorrow, for tomorrow will worry about its own things. Sufficient for the day is its own trouble."
(Matthew 6:24-34)
Seek ye first the kingdom of God and ALL THESE THINGS shall be added unto you. He's referring in that line to everything He just spoke about: food, clothing, and the days of your life. God is the one who provides for you! He gave you that job and if He takes it away He will provide another path. The journey may be difficult and you may wonder why your road is so rocky but remember the goal! We will never learn to trust in God if we never have to. Trials and lean times are necessary as they force us to look to Him. Our holiness is the point of all this, life is meaningless apart from that one bit of truth! If your life becomes more difficult than it is likely that your present circumstances were necessary either for your sanctification or for someone else's.
We can go on when everything seems to be falling apart because we know who is holding it all together. We can keep working when it feels pointless because we know that the point of our existence isn't in that paycheck, or that promotion, or that relationship; it's with God.
"...a thorn in the flesh was given to me, a messenger of Satan to buffet me, lest I be exalted above measure. Concerning this thing I pleaded with the Lord three times that it might depart from me. And He said to me, "My grace is sufficient for you, for My strength is made perfect in weakness." Therefore most gladly I will rather boast in my infirmities, that the power of Christ may rest upon me. Therefore I take pleasure in infirmities, in reproaches, in needs, in persecutions, in distresses, for Christ's sake. For when I am weak, then I am strong.
(2 Corinthians 12:7-10)