A common misconception about Christianity is that if a person will "ask Jesus into his heart," the person's life will become oh so much nicer and easier.
I repeat...that is a misconception.
One reason a person's life generally does NOT become more comfortable or easy when they become a Christian is because becoming a Christian involves becoming more Christ-like...and becoming more Christ-like involves personal change...and most people aren't really all that excited about change, especially personal change.
Not surprisingly, C. S. Lewis wrote an excellent analogy that helps to explain the process and why it's not oh so nice and easy. From Mere Christianity:
Imagine yourself as a living house. God comes in to rebuild that house. At first, perhaps, you can understand what He is doing. He is getting the drains right and stopping the leaks in the roof and so on; you knew that those jobs needed doing and so you are not surprised. But presently He starts knocking the house about in a way that hurts abominably and does not seem to make any sense. What on earth is He up to? The explanation is that He is building quite a different house from the one you thought of ― throwing out a new wing here, putting on an extra floor there, running up towers, making courtyards. You thought you were being made into decent little cottage: but He is building a palace. He intends to come and live in it Himself.
Truth is...Whether we're talking nutrition, cardiovascular health, vocations, or spirituality, for any change to result in a long-term benefit, it generally will require some short-term discomfort...to put it mildly.