1. The problem in hand may not have a good solution. This is especially true of research type problems. You have to pick the right one, otherwise it can be a frustrating experience. This is where a broad knowledge of the subject and previous research help.
2. Some potential solutions may be very difficult to implement or explore, so one tends to explore the simpler options first. When these are not enough, you tend to loose faith.
1. The problem in hand may not have a good solution. This is especially true of research type problems. You have to pick the right one, otherwise it can be a frustrating experience. This is where a broad knowledge of the subject and previous research help.
2. Some potential solutions may be very difficult to implement or explore, so one tends to explore the simpler options first. When these are not enough, you tend to loose faith.