Another reason why you can't focus is procrastination
. Procrastination is the willful and unnecessary postponement of making decisions or doing certain tasks. Even when you are aware that something needs to be done, you choose not to act on it, which then leads to free-floating anxiety knowing that something is yet to be accomplished. This is usually a response to overwhelming tasks or decisions. It may also be due to a poor setup of your surroundings and a lack of discipline where you cannot delay gratification. Check out this link
to know more about how to stop procrastinating.
You could also be physically or mentally tired
. When you experience fatigue, both physical and mental exhaustion, you can have trouble focusing. It is one thing when you are physically tired – sleepless, hungry, weak, or sick – but it's another thing when you are mentally tired – too much to think about, depressed, anxious, and so on. This kind of tiredness makes it very difficult to concentrate. Studies show that when mental fatigue persists, it can lead to a full-blown burnout, physical ailments, and stress-related illnesses.
The fourth reason could be due to a lack of motivation
. When you find yourself disengaged with the things you need to finish, it becomes difficult to concentrate. You cannot focus when you don't value the reward you get from performing the task. This is common when the main motivation is extrinsic. Furthermore, not all people have the same level of achievement motivation. Some people may be inherently more driven and motivated than others, which explains why they focus more on pursuing their goals.