They say procrastination is the thief of time, but it does more than just waste minutes (or hours) you could spend being productive. The longer you procrastinate, the more work-related stress builds up and the magnitude of the task ahead begins to feel larger and larger. The most effective remedy I have found to treat procrastination is to simply make a start.
Getting the ball rolling by pulling up the assignment sheet and opening a fresh document to start with does wonders for the work mindset. Despite their ease and straightforwardness, taking these small steps is often enough to give you the sense of direction and agency needed to crack on with the task at hand. In the past, I have spent hours messing around on my computer before making these most modest accomplishments only to find that's all I had to do to switch into work mode.
If the assignment is longer and you're spending multiple days on it, set yourself a small step to complete first at the beginning of each day to help you find focus. The easier the better: making it something that requires little time and cognitive effort will ensure you get it ticked off and move forward. Something I like doing for essays is pooling the resources I need to start writing, which in my case is scientific papers and lecture notes. I do this accompanied by music and my morning coffee, which helps me ease into the working day.
Managing your time
Life is, of course, more than just a sequence of assignments and deadlines. You probably have other things happening which take up time, related to school/work or not. You should not neglect doing the things you enjoy in order to take an 'all-in' approach to assignments. Your work will generally suffer, and your mental health and motivation will follow suit - both of which are vital to long term attainment.
Having said that, it is essential to structure your time such that you can get the most out of your working self whilst continuing to do the things you find enriching and rewarding. A good way of maintaining a healthy balance in this respect is by starting your work a decent length before the deadline. As opposed to cramming your efforts into a three-day slog before submitting last minute, this approach allows you to split your days between work and leisure, so you don't become overwhelmed and feel like you have to give up your life to do your work.
I personally find it's best to start the day with a small bit of work, usually just some light 'box-ticking' tasks, then taking exercise and coming back afterwards to tackle the denser components, before socialising or watching a film or something else leisurely. Exercise has numerous benefits for brain function and productivity (see here) which is why I like using it to break up my work periods. Furthermore, because it's active rather than passive leisure it upholds the productivity mindset - helping you drop back into the working rhythm more easily afterwards.
Using a calendar to chart your assignments is a good way of staying on track and on time. Don't just include deadlines (though definitely do this to avoid congested work periods) but plan the days and periods you'll spend on each piece, and even better, include details for those periods about what specifically you're going to get done. This second part can be done just the night before; knowing what you need to do with your work before the day has started improves your chances of executing it.
Sometimes clashing heads with the content is what stops us from moving forward with assignments. It can feel daunting to ask supervisors and staff for guidance, but with them you share a common objective and they will be happy to help. Sometimes it just takes the mastery of one small concept to unlock a whole field of understanding.
Likewise, consulting friends and colleagues if you're stuck is always worthwhile, not least for solidarity alone. They might be able to help you get to grips with the work, and maybe you'll be able to assist in return. They may well be struggling with it themselves! Having a healthy and supportive rapport with your peers is positive for all involved and is something to find reassurance in.
If it gets to that late stage where you feel stuck in a hole, the challenge ahead is insurmountable and your head is swimming through waves of stressful negative thoughts, contact your superior and tell them you're struggling. It is not the end of the world and they will help you put a plan in place. Circumstances permitting, they may grant you an extension as well. Just don't let it become a bigger problem than it needs to be!