They only advice I can give you is there is no trick or fix. You are going to fail and that is okay. You have to think of it like a muscle. You don't start with 600 lbs weights. You start at like a 6 lbs weights and work your muscles up.
Building focus is the same way create very small goals maybe it's write one paragraph of your resume then stop. You built up your motivation muscle just a little bit.Then when that becomes a habit add more goals and maybe bigger goals as you go along.
The biggest issue I find is people make goals around results and sometimes those results are not in your control. So people think they failed their goal and got discouraged but framing your goals about what you are doing keeps you going. As you celebrate the accomplishment of the journey of doing not achieving as that is just a byproduct of what you are doing.