Just as reciting a blessing is a good thing at the appropriate time, so, too, there are times that it is better to not recite a blessing. For when it comes to blessing Hashem one must very careful to not recite an “unnecessary blessing” or a “wasted blessing,” since one who does so transgresses the prohibition of Do not take the Name of Hashem, your God, in vain (Shemos 20:7). By consulting the wise one learns when it is correct to recite a blessing and when it is not.
Similarly, when it comes to blessing one’s fellow, there are times that it is forbidden to extend a blessing:  It is forbidden to greet another with “Shalom” or to bless someone before praying Shacharis (the morning prayer);  Sometimes by blessing another person in front of others, it actually causes that person harm — if the blessing was in response to some favor, the other people present might start to ask that person for favors thinking that they also deserve favors from him. All this could lead to discord and resentment. Therefore, the wise person acts prudently and whenever there is a possibility that he might cause harm to the other fellow (if his good deeds become known) he acts like the faithful of spirit who conceals a matter (Mishlei 11:13).