Feeling out of control in your life can have profound effects on your physical and emotional well-being. Here's a start. Write down every role you play and the needs they fill. You may be a sister, a daughter, an employee, a friend, a believer, etc. Set some goals for change, and revisit them on a regular basis as a checkup to see if you are doing what you need.
Priorities shift, of course.
Some of us go through phases where school is the most important thing for us, or friends. Later, our families are often most important to us, or a spouse or significant other. These relationships may pull on us uncomfortably when we want them to shift. Think as objectively as you can about what is at stake for both sides in such debates, and think, too, about how you can make it easier. If your friend is having trouble accepting a new boyfriend, perhaps it is because she misses how close the two of you were when you were single.