Create a list with all the tasks you want to complete on each specific day, and prioritize them.
Check that list again and make it more realistic: it should ideally contain a maximum of 2-3 major tasks. Reaching small daily goals is an unknown secret to master productivity and focus!
Find a playlist that you like and relaxes you. Depending on the type of work you have to do, you may want to opt for instrumental music.
Take a 15-minute break every 90 minutes: stand up, have a little walk, or simply daydream.
Make sure you eliminate unhelpful distractions (put your phone on airplane mode and keep browser tabs strictly limited to the tasks you’re doing).