I have diagnosed ADHD and with that for me, time works very differently. For me it's always Now/Not Now - these are the only two dimensions in my psyche.
For me two things that have worked, really well are
1. Writing down the day's goals every morning, as
@t2van recommended.
I maintain two lists on pages side by side in a diary, dedicated to just doing this.
Left are chores. I include everything - even driving myself to work. Or hitting the grocery store. Or prepping meals. Or hitting the gym.
On the right are work and work related deals. This also includes everything. If I have a mail from you, one of my entries would be "Respond to INCC's email".
If I have a major task, I'll add the task name as a title and everything I intend to do about it as entries under it.
There is something gratifying about striking the list off. And if you end your day with a lot of strike-offs, you get such a high and such low anxiety levels, it's amazing.
2. Using a Pomodoro timer
I tried Pomodoro software but that ended up not working. I then bought an actual Pomodoro timer.
I have this exact one.
All of my work tasks are divided into Pomodoros (25 mins windows)
After every Pomodoro, I take a 5 min break.
I get up and stand at the Window and stare somewhere far. This unfocuses your eye and helps reduce eye strain. I go and sip water. Check my phone for texts etc.
After every 4 Pomodoros, I take a longer break of 15-30 minutes. This is when I browse forums, or read something interesting. Or go grab a cup of Chai (Tea). Say Hi to others in the office building.
15 min breaks if I was doing light work. 30 mins if I was doing hard work.
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Every productivity app these days is useless. I joined r/habits on Reddit with high hopes.
But apparently building a productivity app is the "Hello World" of vibe coders. Because everyone and their mothers is building one and spamming that sub with it.