Assumption: A resumé is a personal history, and prospective employers will read it primarily to learn about past jobs and accomplishments.
Replace with: A resumé is best thought of as a proposal, rather than a history.
Although a resumé does primarily include information about your personal history, its chief aim should be to convey this information in a way that is highly relevant to the job in question. Thus, the key question to address is: How are you uniquely qualified to do well in the position for which you are applying? Writing to answer this question can turn a dry personal history into an attractive employment proposal.
Assumption: My resumé probably won't be that important anyway–it's connections and luck that will get me a job.
Replace with: Revising and improving your resumé can play a central role in landing your next job.
No reasonable person would deny that connections and luck help. Nevertheless, not everyone has or finds the right connections, and not everyone wants to wait on luck. Take the initiative, instead, to craft a strong job-search strategy, and include revising your resumé as a central piece of this process.
Doing so, at a minimum, will accomplish three things: 1) you will gain clarity on your strengths and all that you have to offer in your next job, 2) you will have an important vehicle for introducing yourself to potential employers, and 3) you will have a springboard for a strong interview.
Assumption: The previous version of my resumé was good enough, and probably needs very little done to it.
Replace with: Just about any resumé, even one used with success before, can benefit from careful scrutiny and periodic revision.
Your resumé should evolve as you do. In addition to acquiring new skills, experiences, and accomplishments, you may have shifted in your professional focus or interests. Perhaps you have gained insights into what employers are really looking for in your line of work.
Above all, your resumé should be revised so that it is tailored to the employer who will receive it. Even if you have little to add in the way of content, you can always improve your resumé by refocusing it on the specifics of the position you are seeking, and by strengthening its wording and overall appearance.
The bottom line (a winning perspective):
Take on the task of writing or revising your resumé with the conviction that any resumé can be made stronger, that you have an important employment proposal to bring to the eyes of potential employers, and that doing so can be the avenue for landing the job you want. It is with this perspective that you will produce a resumé good enough to open doors!