Writing a thesis is totally different than taking courses. No more lecture hours, no fellow students in your class. Some students therefore get stuck in their thesis project: the required work seems too much, there is no clear working schedule, etc. I therefore (strongly) advise the below steps.
(Note that all advise is personal, and your own supervisor may disagree)
Intended for: BSc, MSc, PhD
1. Sit at university
Ask for a work spot within the research group. The bachelor/master students who do this usually florish. You get to know the other students (BSc, MSc and PhD), and before you know you enjoy having lunch with them every day. Their peer support will also help you through the thesis process.
(The same actually applies to PhD students: come sit at your university workspot every day. It's the best way to maintain clear and healthy boundaries between work and leisure: you work at university, otherwise you're off.)
2. Take a workweek approach
Promise yourself to come to university every monday-friday 9.00-17.00, to work on your thesis (and of course take your breaks). This seems heavy compared to your course schedule, but your future job will demand the same thing. Outside of these hours (incl weekends), you are free. This helps you maintain healthy boundaries between study and leisure, and your thesis progress will be enormous.
3. Prioritize your thesis (empty your agenda)
A common mistake is to have too many things on the side: you still have to take two courses, you are TA in a certain course, you are part of some student committee, etc. In my experience, you results decrease stronger than linear with every hour less you can spend on your thesis per week. Your switching time simply becomes a too big burden. To make progress on a big project you need connected days, or even weeks, to fully work on the project. You can slowly start your thesis in a semester in which you still take courses, but to really push the project, ensure an empty agenda.
4. Stick to your timeline.
Students often consider a timeline a useless effort ('We don't know how the project will unfold'). This is not true: being able to stick to a timeline is actually an important part of any type of work. You should learn to estimate how much time a certain project will/may take, and whether that is feasible. Of course, you may need to adjust (drop a research question, extend your project), but in general it should be feasible to deliver a thesis in the proposed time. If your thesis should take 6 months but you are already at 2 years, then you did something wrong (Note: planning and timeline is always part of your grade as well).
5. Ask for the research group meetings.
Your supervisor is probably part of a research group, which has some form of weekly group meetings. Here, PhD students present their work, or the members discuss a research paper. Joining this meeting can help you a lot: it is a break from your thesis work, you learn about your topic, and you can chat with other students who can actually help you out with your work.
6. Meet with other thesis students.
If there is no research group (with meetings) available, a good alternative is to meet with fellow MSc studenst who also work on their thesis. Ask someone from your year whether they want to work together for one day a week. You can talk about the struggles of a thesis, take breaks together, and maybe even think along with eachothers' project. (Sometimes your supervisor can even facilitate this among his/her students, for example in the form of shared supervision meetings)