Less is more assertive.
Here's the fastest assertiveness training: four words to usually not tell your boss . . .
Usually say that something is, not that you feel it is.
Besides injecting doubt, "feel" injects emotion. True, when your general manager commends you, it's better to respond "I feel great" than "I am great." For most professional purposes, though, "feel" sounds gratuitously emotional, self-indulgent. Your GM wants to know how the new satellite truck is working out; not (Alan Alda notwithstanding) how you feel it's working out. In particular, if you're a woman in a sexist environment, "feel" engenders the reaction "She's speaking from emotion, caprice, how she wishes things were -- not from facts."
Barely more assertive than "feel" is "think." "Think" is at least up from heart to head. But "think" still injects doubt:
The philosopher Descartes said, "I think, therefore I am." I add, "I say 'I think,' therefore I am wimpy."
If "feel" and "think" are often wimp words, is the cure to know? No. "I know" (and its variants) overcompensate:
Occasionally, of course, you must show uncertainty. It would be reckless to say flat-out, "If we hire that anchor, our ratings will be up six points in a year." Even here though, don't say "I feel [or even "I think"] that if we hire that anchor . . .." Rather, objectify your uncertainty: "If we hire that anchor, our ratings will probably be up six points in a year." The assertive word: "probably." As in that respectable science, probability.
Indeed, make the most of uncertainty. Instead of telling your GM, "Given the level of audience response, I think we'll prevail," try "This level of audience response usually spells victory." The assertive word: "usually." Your GM doesn't expect you to be a fortune teller, but is impressed when you apply to the future the probative evidence known as your professional experience and judgment.
If you're only 80% sure you'll have that blockbuster series ready for sweeps week, bypass the wimpy "I think" (and the irrelevant "I hope"). Rather, capitalize on your status as the world's ranking expert on your current state of mind: Say "I plan to have it for sweeps week." George Bush's convention speech of last month sounds assertive. You know a big reason why? In those 4,500 words, Bush says "I hope" and "I think" only once each (in adjoining sentences, coincidentally): "And I hope to stand for a new harmony, a greater tolerance. We've come far, but I think we need a new harmony among the races in our country." That's vice presidential. Here's presidential: "And I plan to stand for a new harmony, a greater tolerance. We've come far, but we need a new harmony among the races in our country."
In summary, usually omit "I feel" and "I think" on the one hand, and "I know" (and its variants) on the other. On the rare occasion when you must show uncertainty, try "probably," "usually" or "plan." . . .
Radio-Television News Directors Association Communicator, 9/88, p. 22.