One concept I never understood was "saying no to say yes later". How can saying no to an opportunity actually help?
For most of my life, I didn't understand this quote at all. Some of my favorite activities had parts I didn't like (even golf has the occasional 3 foot putt now and again)...of course, no opportunity would be "100% right" or a perfect fit. This isn't really what that quote was about.
It took me until my freshman year of college (and a club rejection) to really understand what that meant. Sometimes, there are opportunities are that may be prestigious or exciting, but completely not right for you right now. Maybe you aren't ready, or maybe you have realized the costs outweigh the benefits of a position/opportunity.
Whatever the case, you may feel guilty or unhappy about even considering a "no". You've worked hard, and it seems like it is the right thing for you.
The thing is that a large time commitment can take away time and energy from the things you are actually 100% happy about.
I don't even know how many opportunities I missed when I was busy doing things I liked! I did know that I never wondered about what I missing out on...