Krsna reiterates that it is not easy to control the mind. But if you use your existing intellect to withdraw just a little and back it up with constant effort you will eventually succeed.
Whether you are a gymnast, musician, architect or scientist this is the pathway to excellence. No achievement comes effortlessly. Every success story has years of hard work, constant striving and failures behind it. There is no such thing as instant success. In the spiritual field the results are subtle and take time but you are assured of success eventually.
Arjuna now asks what happens to a person who does not have enough self-control but has shraddha. Realistically, perhaps one in a million people on the path of spirituality attains Perfection. Arjuna wants to know what happens to the others.
Usually a person starts the spiritual journey in all sincerity but somewhere along the way loses focus and goes astray. Or one may rise to a certain level and give up because the path gets more difficult.