Well, I can only say that you are not alone. I too am very slow in my thinking. Am sure there is nothing wrong with my comprehension or application skills. But, I need my time. To put it better with an example, if I have huge amount of time, I know how to find the best move in a chess match. But, there are millions around who will find that best move much faster. When I asked around the same question, I found these interesting points.
Firstly, almost everyone said, practice more. Perhaps, practice improved their speed. I had a hard time memorizing 8 * 7 in my childhood. I used to do 8 * 5 = 40 first. Then add 8 twice to it. But over a period, I realized that if I have to calculate it 100 times in a week, I will eventually remember it. So, I did accept the point. Yes, practice does matter.
But, this still did not answer my question. How come, the other kids could do 8 * 7 in the first attempt? This is when I realized the second and bigger secret. Pay attention to this. First time, I memorized the 8th Table, I took a shortcut. I studied till 8 * 5 and then I knew that I can always use addition trick to answer. That one day of laziness had cultivated this bad habit. Now, my brain refuses to memorize it. Again, I can take a chess example here. In chess notation, a1 is the left bottom square from where white plays. b2 is diagonally above a. So, you go one step right and one step upwards from a1 to reach b2 and so on. Fairly easy stuff. Now, when I learned this notation, I used to calculate from a and 1 and then narrate the square. It just became the habit. While some kids memorized the squares, I was calculating it. A bad habit. It led to humongous cost. I was so slow in taking notes during a game.
Alright, now I understand what slows me down. But, how to improve it. Breaking these unhealthy habits is not easy. Luckily, there are several ways we have known already. Know your habits, target them with training. Nowadays, I spend several minutes just visualizing and thinking differently about notations. Another thing you could do, is try a bit of meditation. Am not joking here. In a way, we are addicts of compulsive behavior. Our mind knows that it must change but refuses to change. The best solution is to take some time, give our mind a rest. Clear it off. Then, try again. This works. I spend around 15 minutes whenever I get time, to just stay still and relax. Finally, the best of all ways, is to find a purpose or a passion. The stronger your passion is, you will find innovative ways to circumvent your problems. If nothing works, only one thing can save you, God! Really, I am not kidding. Transcendental purpose has supernatural powers. For me, helping students is my way to find a spot in heaven. It is my dharma, my duty. It gives me transcendental satisfaction and fulfillment. I have conditioned my mind to believe that my purpose of life is to find a smile in a student, promote computer science and play chess. You may have different purpose; but if you believe in God, then all the above can be sidestepped and you can still win.