Breaks are necessary for every kind of concentration. Your brain tends to focus best in the first 5-15 minutes of starting a task and 5 minutes before ending a task. In between it will zone out. So if you do a task contiguously for 2 hours with no break, you'll probably just get ~20 minutes of truly productive work. For very difficult/tiring tasks, you also need to allow your mind some 'rest time' for the information to 'settle'. As with exercise, pushing yourself too hard accomplishes nothing.
The length of the break varies. The Pomodoro Technique recommends 25 minutes of work followed by 5 minutes of break (rest, breathe, stretch). Many people find the Pomodoro system to be optimal, though I find the 25 minutes far too short.
Sometimes 30 mins work/30 mins break works (watch a series after a study burst). For complex work, I find that 45 mins work/15 mins break works best. One of my roomates, who was top of his class at one of the continent's top universities, did a routine of 30 minutes of study followed by a 30 minute episode of some comedy show.
Start with the hard stuff
You have a limited amount of willpower every day. Eat the frog first. Don't waste your willpower reserves on trivial things or arguing with strangers on the Internet. You will have some very difficult things on your things to do, make sure you accomplish at least one every day.
No doubt you'll want to relax, so save the relaxing/light things to do for the end of the day.
Chunk it down
If if you can break it down into smaller parts, do so.
The brain can only focus on 4 things at once (older studies say 7 +/- 2). But there's a limit and the easiest way to work around that limit is to keep as little of it in your head as possible.
Learn to Read
How to Read a Book, by the philosopher Mortimer Adler will save you a lot of time if you're a heavy reader. For someone doing a hardcore liberal arts course like Philosophy, this is even more helpful.
The book assumes that you have mastered elementary reading, but goes on to explain how to skim and see if a book is worth reading, how to squeeze every last bit of knowledge out of a book, and how to compare different books.
Perhaps one of the most important things to take is that your first reading of something difficult should be contiguous. Don't look up terms. Don't backtrack or reread. Just read a whole chapter or subsection by itself, and then go back to the start and figure out the terms. Quite often you'll understand what something means when you see the big picture and the word used in context.
Get a proper diet
It's very common for students to skimp out on food, to save time and money. Don't. Your brain functions on glucose and glucose from food only lasts about 4 hours or so.
This doesn't mean that you can live off snacking with sugar the whole day. It means you need a constant supply of proper healthy food about 3 times a day. Make sure you start the morning with a decent breakfast... otherwise you'll be braindead on the low sugar after not having eaten in hours.
Get enough sleep
Sleep converts short term memory to long term memory. If you're sleepy, it means your brain is about full. Try and take a nap if it's too early to sleep. At night, sleep is the most productive thing to do.
Build a habit
Everything is difficult the first time. It took you months to learn to walk and recognize a person's face. It took you years to learn to read. But given intense time and practice, you can do these things without thinking.
Learning to focus intently is just the same. The trick to building a habit is to simply repeat the same thing over and over, many times, and it gets easier each time. You should 'anchor' this habit to some kind of cue to pick it up more quickly, like a favorite song, office environment, time of day, or the winding of a Pomodoro timer. A lot of students set the cue to their local library.
You should also avoid developing bad habits. If the first thing you do every morning is surf Reddit, and you've been doing this a hundred times, it takes a lot of willpower to do work first thing in the morning.. probably more than a hundred times of forcing yourself into it.