”Take the example of a person learning how to drive a car. The first few lessons are very difficult but as one perseveres, controlling the steering wheel, using the various pedals and keeping an eye on the road at the same time becomes less daunting. In fact after some lessons it actually becomes quite easy. With experience one can converse, observe everything outside and at the same time maintain complete control of the steering wheel and the pedals.
Now if this person was to give up after the first few lessons would he ever achieve a driving license? The answer is no. He would end up using public transport for the rest of his life. In fact knowing that being able to drive is an absolute necessity, a person will try again and again even after failing ten driving tests. Not just that but he will turn to Allah subhaanahu wata’ala and ask for assistance and will even get others to make the same du’a. This is so in all fields. One perseveres knowing that success will follow only if one exerts effort.
Likewise to refrain from sin is undoubtedly very difficult in the initial stages. Hence one may want to give up despite the desire to become a Muttaqee (God-fearing person) and refrain from the disobedience of Allah subhaanahu wata’ala. It will undoubtedly be difficult in the beginning however it will get easier and easier until it will become a part of you. This will only happen after effort and striving. Then and only then will one become a Wali (friend of Allah) and a true Muslim.”
Source: http://shaykh.wordpress.com/2010/07/01/effort-leads-to-success/#more-5000