Christianity solves a couple of "personal" problems. It solves our struggle against sin (this is called sanctification), and it solves the problem of our well deserved awaiting judgement (this is called justification). It also empowers us to further the kingdom of God.
Mark 11:24 (NASB)
24 Therefore I say to you, all things for which you pray and ask, believe that you have received them, and they will be granted you.
In saying this, Jesus did not intend to place himself inside a genie lamp to fulfil our every whim. When Jesus says "all things for which you pray and ask", there is an implied qualification on the "all things". That is, what you ask for must be in accordance with God's will.
This concept is clarified if we take a look at 1 John.
1 John 5:14-15 (NASB)
14 This is the confidence which we have before Him, that, if we ask anything according to His will, He hears us. 15 And if we know that He hears us in whatever we ask, we know that we have the requests which we have asked from Him.
Here, John makes the qualification explicit. What we ask must be in accordance to His will. In James, we see something similar:
James 4:3 (NASB)
3 You ask and do not receive, because you ask with wrong motives, so that you may spend it on your pleasures.
James's audience did not receive, because they did not ask in accordance with God's will. They asked selfishly, in order to fulfil their own desires, and not to further the kingdom of God.