On time restraint When you have a time restraint, your best strategy for sticking to it is making it known. Once you vocalize it, when someone decides to take more of your time it becomes an ethical concern rather than a selfish concern of you saying, "I have to go." Explain beforehand that you only have a few minutes for a call and limit the conversation to that! You had to get on the train and you were rushing to finish up your call, but once you told the person on the other end your situation, you were able to wrap it up quickly. Communication is key.
On daily practice If you can break a massive task down to smaller portions that you can complete daily, you'll be much more apt to finish the entire thing. It's all about finding things to start rather than feeling distanced from the end result you so desire. For example, write a book a page a day, if you can structure it to work as such. You might dive into a topic by writing 365 epistles about it, once a day for a year. Daily practice can make large amounts of progress mindless compared to taking it on in one big swoop. You could put in five mindless minutes a day of writing 300 words of a book and at the end of a year have over 100,000 words. Not to mention, some things require you to make daily progress or maintenance. You cannot neglect your language learning for weeks on end and then "finish" learning all in a few hours. You have to put in time every day and then build on what you created the day before.
On insignificance The less time you spend outside of your bubble, the more you will forget how small and insignificant you are in the grand scheme of life. You might find this depressing at first, because it sounds like something you should be down about, but it's the complete opposite. You should be more than pleased that the world doesn't rest on your shoulders, nor does the rest of the world care to rest on your shoulders. By expanding your perspective (whether that's through travel, talking to new people, or any other out of the ordinary venture), you will discover how small you are becaus ethe rest of life is so l arge. That doesn't mean that you become any smaller, only that you realize where you fit in to the rest of what matters.