It can often stay focused throughout the day, Especially if you have ADHD Or ADD. But regular people often need help maintaining focus as well! We can often make changes to our life and our environment to ensure that extra focus.

ENVIRONMENT

While you may not be able to edit every aspect of your environment. Like a loud neighbor or roommate. Many things are within our control Having a clean and organized area makes a big difference.
If you work better with music, use it. Or silence uses it. You may enjoy working in other places like Starbucks Or a library. Or even outside. Pay close attention to the environment your in, To decide what works best for you.

NO Multitasking

Multitasking is not good for productivity. When you are multi-tasking, What it implies in not accurate. You are not "successfully" focusing on a variety of things at once. Instead, you are shifting focus between things in a quick manner.

This is hard in your brain, and it causes productivity loss.
Our brains are most efficient focusing on one thing at a time, not ten things at once.

Say no To People And things

We say yes way too often. This can drag down our focus when we have so much on our plate. By being willing to say no to people asking us to do extra tasks and tasks we know we won't be able to accomplish easily. We can maintain our focus on the things that matter.

Take Breaks

Taking breaks is important in order to keep your focus. Maximize your breaks by doing something you can be mindful in.
Fold laundry, Take a quick walk. Relax your brain.

Habit stack

Habit stacks mean you have more than one habit that you do in succession. Doing this is extremely effective. You can build very powerful ones overtime with practice.

You can then focus on the more difficult tasks.

Mentally visualize the task

Sometimes if I know I have a tough task the next day, I'll visualize each step and how I'll execute the action. This allows me to accomplish the task with ease. Do this to make focusing much easier.