How to Get a Big Head in Academia
Step 1: Get a tenure-track job at a research-oriented institution.
Step 2: Publish some stuff.
Step 3: Get tenure.
After Steps 1-3 -- which are, admittedly, something of a challenge -- the rest comes naturally!
Step 4: Read some stuff. You might especially find yourself reading material related to the subtopics on which you yourself have been publishing -- especially if any of that material cites your own work. The stuff that you choose to read will become especially salient to you in your perception of your field. (So also, of course, are your own publications.)
Step 5: Attend some meetings. The talks you see, the people you gravitate toward, will tend to discuss the same things you do. The field will thus seem to revolve around those issues. If other presenters in your area know you are around, they will be especially careful to mention your important contributions. You might even be sought out by a graduate student or two. That student or two will seem to you representative of all graduate students.
Step 6: Acquire some graduate students. They will tell you that your work is terrific and centrally important to the field.
Step 7: Read some emails. The people who like your work and think it is important are much more likely to email you than the people who ignore your work and think it's crappy. Also, the content of people's emails will tend to highlight what they like or, if critical, will frame that criticism in a way that makes it seem like a crucial issue on which you have taken an important public stand. (Additionally, the criticism will almost always be misguided, demonstrating your intellectual superiority to your critic.)
Finally: Given all the valuable input you have received through reading, attending conferences, talking to graduate students, and professional correpondence, it will seem clear to you that your field (post-Schnerdfootian widget studies) is central to academia, that the issues you are writing on are the most important issues within that field, and that your own contributions are centrally important to the academic understanding of those issues.
Sadly, your colleagues will not seem to fully appreciate this fact.