Two roads diverged in a wood... I've narrowed my choice of what master's degree I want to do down to two. One is urban planning, the other is more about engineering and infrastructure policy. The former is the safe choice, the latter is a big challenge (math) but has more interesting courses. I keep changing my mind between the two options. How do you know you're good enough to climb the metaphorical mountain? People around me say that I can, but I'm not confident about it. While I ponder over that, I've got more than enough work to do in the next two months. Two courses, two large theses and I've been appointed Treasurer of a club/organization I'm part of this week. Busybusybusy...
I agree - keep in mind though - if you know the urban planning is a safer choice - it may give you more time to pursue extra-curriculars/other career-related activities (meetup groups, personal projects, etc). Don't discount the ability to be flexible either! There are many ways to the top of the mountain!
How do you eat an elephant, veen? One bite at a time. Don't avoid doing something just because you're scared of the amount of work.