There is no doubt, based on my experience over the years, that academic achievement is tightly linked to a person's ability to focus on a task and see it through to completion. Some students believe they aren't smart, or that they are unable to succeed at academic work. Some students believe they were born that way. Some students credit a bad experience in education for why they struggle with academic subjects or tasks. What ever the case may be, there is a mountain in the way of some students learning. Often, students have planted themselves at the base of their mountain and set up camp. There at the base of their learning-mountain, they sit around the camp fire with their parents and friends, telling and retelling the story of why they "just can't". Other students see a mountain and are determined to surrmount it, because once they have surmounted a mountain, they know they can surmount any mountain.
The challenge is to get the kids who are camped out and caught in their self-sabotaging cycle, to understand that they can surmount a mountain... it's just one step at a time. The key is to keep taking the steps, despite fatigue, distraction or personal desire. One. Step. At. A...Time.. and again.
Helping kids climb mountains isn't all that hard. First you have to remind them that they aren't looking a mountain, they just think they are. Sure you can tell them that, but they won't listen yet... so here is what you do. No matter how mundane or challenging the task ahead of them is, remind them that the task is still preferable to being illiterate. I've never met a child who didn't want to be thought of as intelligent, when they understand that an academic task is theirs forever, knowledge gained is never lost, and therefor isn't a waste of time, but in fact is another $100 in their literacy wallet (just another analogy) they stop viewing lessons as mountains, and start viewing lessons as... well.... possessions. Theirs. Theirs to do and keep, and that knowledge can't be taken away.
The second the thing you can do is answer their questions, no matter how small. Answer their questions as though their questions are brilliant and intriguing, To them, their questions are intriguing.... or they wouldn't be asking it. If they are asking a question they already know the answer to, answer it anyway. Sometimes these students just need confirmation. If you answer every sincere question they ask, they will learn to do this for others. When they get something correct, praise them as though they have surmounted a mountain, praise them genuinely. For these kids, getting it right may have been surmounting a mountain. If they get it wrong, praise them for trying and stay with them, give them a moment to think as you kneel quietly beside their desk, and see if they answer again on their own, correctly. If they don't, then ask them if they'd like to work it out with them again. Don't teach them or explain to them, but work it out beside them and with them, let them see your steps over the mountain so they learn to think in a way that yields learning.
It's only for a short time that you need to stand with these kids and look at the mountain. Before long, they'll be surmounting it on their own, and you will have been the fortunate one who got watch them embark on that journey.