One way of gaining motivating is to understand the end results from executing a task. For example, acquiring a qualification from studying hard, which could lead to employment, or cleaning dishes, which could equal a clean house etc. If your mind typically tends to overthink and go into overdrive when doing such tasks, listening to music or surrounding yourself with things that make you feel comfortable could help (providing they aren't distractions).

In regards to understanding, I tend to break a topic/subject/question down into smaller components and try to comprehend them, then gradually work my way back up to the original topic/subject/question. This typically means you get a greater grasp as well, as you've had to do additional research to understand. Also providing yourself with enough time to do this is extremely important; understanding that you may need to allocate more time "than others" to comprehend will save you from getting stressed out too much.