Just keep a file of letters, e-mails, annual reviews, notes from bosses and others, and other proofs that you're doing a good job. Then your accomplishments testimonial will be ready when you need it. That's altogether different from reciting accomplishments pertinent to the occasion. Citing relevant successes to your boss during a review, to a meeting when you are pressing a point or to a prospective employer is not only acceptable, it's strategic. Desperate people and the self-absorbed call contacts out of the blue just to tout their latest accomplishement.
Smart promoters do it far more gently.
At the same time they briefly fill the person in on something they've been working on. My wife is a writer and her most lucrative project came when I mentioned her career in passing to a person I was working with. Once he knew of her accomplishments he was eager to use her services. The more you keep colleagues, clients, vendors, friends and family informed about what you are doing, the more they can help you find that next opportunity. Willie Sutton once said he robbed banks because that's where the money was.