THE SIGNAL IS NOT THE GOAL
I’ve warned against too strong an investment in goals, if you risk altering your motivations. Self-modification is a dangerous thing, and behavior often leads to belief.  As Pascal might say (and I paraphrase): “Have trouble believing in God? Just go to church.”
Consider your environment carefully, for if you are like most humans, you might start to conform. It’s a subtle process.
But this isn’t the end of the story. Goals are tricky, and you should take care to choose them properly. Sometimes, people mistake signal for substance. I need to remind myself on occasion: the signal is not the goal. Signaling that you’re on a path to Greatness doesn’t mean you’re actually walking it.
When you set a signal as your goal, you misinterpret causality. I have seen undergrads who might say, “Great persons X, Y, and Z got PhD’s from the Ivy League, and so I should do that too.” They confuse cause with effect.
Great people (if they are actually Great) tend to have reasons for doing what they do. They don’t simply follow some greedy function of ambition, snatching up opportunities that look like something in which a successful person might engage. To the extent that a Great person signals Greatness with a fancy degree or credential, this signal is often a byproduct of a specific goal she set out to achieve. It is not the root cause of the success, but a side-effect.
Suppose that persons X, Y, and Z are Great Philosophers. In undergrad they studied hard, and wrote impressive things. They had no social life and thought all day about philosophy. Perhaps, these qualities got them into Ivy League PhD programs.
And perhaps (cue the shudder), what made them Great was not their Ivy League PhD programs, but their innate talent and devotion to philosophy. 
Our undergrad ought not to worry about getting into the PhD programs, but rather about studying philosophy. While she also needs to be noticed (signaling never goes away), that is not the main thing. For if she sets the signal (e.g. the Ivy PhD program) as her goal, and spends all her time schmoozing with professors instead of studying philosophy, this will not help her in the long run. Even if she gains entry into the program, she won’t be able to take advantage of the opportunity. 
So I try to be careful. Signaling is important, but it is not the endgame. It does not lead to Greatness.
1 I’m sure that a few thousand books have been written on the power of habit, but I haven’t read any of them.
2 Of course this is not completely true. There are better peers, mentors, and resources at good universities.
3 For similar reasons, most undergrads shouldn’t drop out of Harvard or Stanford, despite the signal this might send (look at those rich founder dropouts)!