Get It Done – I don’t finish tasks in time set aside

My question is how to better schedule my day, to make sure I am in self-integrity.
How do you decide what you will do in a day – what to take on and what not to? I do have a list of steps from the big projects related to my coaching practice that I’m working but I also have a lot of other work that has to get done like personal/family tasks and tasks for my part-time job.
I am in a cycle where I make a list of things to do each day, along with the time estimate for each item. I then schedule the items onto my calendar.
Then, one item ends up taking 4 times as long as I anticipated. I’ve heard you say before to just do it in the time allotted but I’ve noticed that unexpected stuff comes up (eg unexpected technical issues) which extends the time it takes or I just didn’t estimate enough time to get it done.
I end up doing 1/4 of my overall list and the list rolls forward to the next day.
This happens almost daily.
Wondering what I should do – increase the estimate for how long each item will take? Put sub-par work out (e.g. a 1/2 written blog post, or blog post without SEO)?
Some other strategy?
Thanks so much in advance