Thanks Sunflower and Trusylver!
Another victory: I finished organizing my home.
All of the things have been organized, put in a place where they should be. So, if I have to look for something, I know where to find it!
I have been working on this for 2 weeks, and I had already organized 80% by last weekend, leaving me with only 4 big drawers (stuffed to the rim) with random stuff. So, my room already looked organized, and I noticed that it was much easier relax and be productive at home. Throughout this week, I have spent 5 hours or so to get these drawers sorted. Even though this mess was not visible, it was important for me to get this done, because I wanted to give
everything it's own place, and I wanted to see every item, just in case there is something that needs my attention. For example, there might have been an unpaid bill in there, or something else that may lead to trouble, and that idea gave me stress (fortunately there wasn't anything of the sorts

). Now that everything has been sorted, I no longer have that source of stress.
Now my next step is to teach myself the habit of organizing my room for at least 10 minutes per day, right after coming home from work. I have already been organizing every day this week, spending 30-180 minutes per day (because I was still sorting my drawers), so doing 10 minutes per day will be easy. My goal is to get a 30-day streak (of course not counting days that I am not at home), so that I can really build this habit. I expect this to be quite easy; it's much easier to keep an organized home organized, than to organize a cluttered home.
After that, I will pursue other goals. I have made a list of 40 goals or so, that I hope to work on over the coming months; things like "repair my road bike", "organize my computer", "organize my finance", "improve evening routine", "improve morning routine" and, of course, "lose weight". I have written all of these goals in my "Getting Things Done" system (using the Wunderlist web app) and I plan to tackle these step-by-step. So, I don't demand of myself to do all of those goals now, I basically put them in the "Someday" folder, which I check once I have completed another goal.
Now that I have completed this first goal, I have freed some of my time (that I spent working on that goal) that I can spend working on my next goals. My highest priority goals is to organize my finance (developing a system to track my spendings/income, making a saving plan, cutting unnecessary expenses, doing my taxes, etc). I plan to finish this by the end of next month. Also, I have already started repairing my road bike, which will be done by early December. Losing weight also has a high priority, and I will continue improving my eating/exercising habits in the next months; I haven't set a deadline for reaching my goal weight, because I don't want to focus on the numbers; I want to care most about developing healthy habits, and I trust that these will lead to good results; I find focusing too much on my weight (the numbers) just distracting. However, if I would have to do an estimation, I would say that I expect to reach my goal weight somewhere in the Spring of 2017.
By the way, having this long list of 40 future goals (which keeps growing) does not make me feel depressed, quite the opposite, it makes me feel excited that there are so many ways that I can improve my life! I feel that I definitely can do them all, but I do demand myself to be patient and methodical, and not pick up to many goals at the same time, because it is the only way to be successful.