Getting turned down at seventeen tells you about one door on one day. Doors keep opening for decades.

A single no carries far less information than it feels like it does. It describes one group of people, with one set of needs, on one particular afternoon, and says nothing about the decades of other doors still ahead of you. At seventeen the sample is tiny, which is exactly why one result seems to settle everything.

Be disappointed for a day, properly, and then write down what you will try next. Ask for whatever feedback is available and actually use it. Apply somewhere else inside the week, while the work you already put in is still fresh.