Here's an old post of mine from INFP-gc on the subject of dealing with procrastination and getting more productive. It's not really about focusing. In fact, it's just the opposite: it's about being productive by breaking big projects down into little bite-sized chunks of work and stringing them out across a day or a week.
But it works for me.
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I enjoy sitting around and daydreaming or brainstorming (Ne). But sometimes it's time to get off my ass and get things done. To cut off the dreaming/brainstorming (Ne) and get tasks done, I choose a simple strategy and jump up and execute it (Te). Part of the strategy is that I limit my work on the task to 5 or 10 minutes at any one time and then take breaks; that allows me to parcel the work into chewable bites, quit worrying about difficulties to be encountered at later stages of the task, and focus only on the most immediate chunk directly in front of me (Si).
To break it down in more detail:
Extraverted iNtuition (Ne) is an INFP's auxiliary function. In INFPs it manifests itself as brainstorming and daydreaming; and because it's a perceiving function by nature, it resists closure--it prefers to churn and churn and churn without end. That's fine when I want to engage in some productive brainstorming of new solutions or I'm engaged in a fun, wide-ranging conversation with another Ne type. But sometimes all that endless churning is unproductive or even distracting, such as when I'm just daydreaming and should be doing tasks, or when I'm nursing some petty personal insult/injury/grudge and I can't let it go or get past it.
Extraverted Thinking (Te) is an INFP's inferior function. It engages in strategy and execution. It's a judging function by nature, so it dislikes churning and prefers to reach a decision and move quickly to closure and action. It's why ENTJs and ESTJs are so good at managing whole companies and armies. Te is a weak function for INFPs (we're most likely to see it pop up on its own when we're stressed out, in which case it will operate negatively and seem out of control). But with practice, INFPs can still access it in its healthy manifestation in small doses.
Introverted Sensing (Si) is an INFP's tertiary function, and it's the hardest of the main four functions for an INFP to access. It tunes out the big picture and instead focuses on accumulating details; and it's a perceiving function so it likes to churn and play with details without closure.
Okay, so here's how they interact:
It's Saturday morning and I'm in an Ne mood--I want to drink coffee and play on the message board or just watch bad TV programs to see how bad they really are and laugh at them. But I promised my wife that I would do some plumbing work--tear out and replace the guts of the toilet. I already have purchased the new parts and I'm ready to go. But I can't get off the couch and start the work, because whenever I focus my Ne on the task, the task seems enormous and fraught with all kinds of potential complications and problems. It's easier to sit and daydream for 30 more minutes. And then another 30 more minutes.
But then I get a little disgusted with myself, because I know that an ESTJ would be on top of that task like white on rice--the very fact that it's a nasty complex job would be an attraction for him. And I have the same Te that he does (though somewhat less accessible).
So I deliberately turn on my Te and think up a simple strategy that will allow me to spring into action: I'll just take five minutes and *prep* the work. I'll assemble the tools and parts and glance at the first couple steps of the instructions. And then I'll stop there; I'll take a break and I'll go wash the breakfast dishes or go shave or something.
The Te strategy works because it's simple. There are no big decisions to be made in that one little parcel of work, no obstacles to simply getting up and doing it. And I use Si to assist by tuning out the Ne overview and instead focusing on just the details of that one parcel--rounding up the tools quickly and setting up a comfortable and effective work space for the task to come. Then I go shave or eat breakfast or something.
And so it goes the rest of the day. After my break, I repeat the process and do five more minutes of work (review the instructions, shut off the water, and start dismantling the old parts). Then I'll stop and take another break. Then another five-minute parcel.
I focus on one small parcel of the plumbing task at a time (Si), and keep it short and simple so that I have only simple decisions to make for any one parcel and can move quickly to execution. Meantime, I take lots of breaks in between the parcels to do other little tasks around the house. I don't look forward to worry about what comes next, and I don't worry how long the task is taking me (assuming that I don't have any tight deadlines to beat). I look only at the next parcel of work (Si). If I run into a snag on one of the parcels, then I can use a break to apply some Ne to the problem (i.e., go and do a brainless task like mowing the lawn and at the same time ponder where to go next on the plumbing while I mow).
Anyway, hopefully you get the idea. Believe it or not, this stuff actually works for me and keeps me fairly productive over the long-term. And it keeps working on a reliable basis.
Same thing at work. If I'm assigned a 20-page presentation for two weeks away, then I immediately jot a few notes, put them in a folder, and keep the folder at the side of my desk. During the rest of the day and the next couple days I occasionally consider the presentation and jot more notes or do some initial research. At some point, I break open the folder and compile a simple outline from the pile of notes. And so on, building the presentation in 10 or 20-minute bursts of work.
At some point, there will inevitably be periods of intense work on it for an hour or two to do some heavy writing. But that's usually in the second week, and the format and content of the presentation are pretty well solidified in my head due to the previous short bursts of work on it and a week of percolating it in my head in the meantime. By the time I have to do the real writing, it's really just a question of patching together the notes I've already made and then doing some polishing.