If one said, for example, "I will not engage in unnecessary talk" with the intention of not excessively talking about unimportant things but not to completely forbid it, what has he forbidden himself from?

Can such a general statement go into effect?
If so, what if the statement were even more general, that it would be almost impossible to avoid, such as "I will not smile?"

Is it possible that it does not go into effect because his intention does not match the implication of his words -- that he will not talk any words that are not absolutely necessary?

If it does go into effect, has he only forbidden himself from what he intended, or has he also forbidden himself from whatever was implied by his verbal statement?