There was a flurry of reporting (e.g. PhysOrg et al.) a few years ago on the same observation being made by researchers. Speculation was/is that the declaration/statement creates in the speaker enough sense of accomplishment that internal drive to complete the task is lessened. In other words, it already feels at least partially done -- as I remember the description -- and drive is reduced.
Whatever the explanation, I agree with you as to the effect in my own experience. Talking about something not yet done, especially as a goal, seems to be counterproductive -- I'll even use the word "jinx".
Edit: Hmm, on the other hand, having a hard and fast deadline -- especially an imminent one -- can be quite compelling and motivating. I continue to debate with myself to what extend I want to / should put myself into such positions (e.g. purposefully loading up the schedule). However, doing so is NOT the same in my mind as making a big public statement. MY knowing the deadline can be motivating. Talking with others about it can be dissipating.
Whatever the explanation, I agree with you as to the effect in my own experience. Talking about something not yet done, especially as a goal, seems to be counterproductive -- I'll even use the word "jinx".
Edit: Hmm, on the other hand, having a hard and fast deadline -- especially an imminent one -- can be quite compelling and motivating. I continue to debate with myself to what extend I want to / should put myself into such positions (e.g. purposefully loading up the schedule). However, doing so is NOT the same in my mind as making a big public statement. MY knowing the deadline can be motivating. Talking with others about it can be dissipating.