The Biur HaAmarim explains the reason why wine has a special blessing is because not only does it make “Hashem happy” with the wine libations, but it also makes people happy for it caused Yaakov to receive the blessings when he gladdened the heart of Yitzhak and the shechina [“G-D’s presence”] rested on him.
The Kol HaRamaz points out that the reason why meat doesn’t have its own unique blessing is because Esav also brought meat and in fact Yitzhak did not ask for wine, and neither did Rivka tell Yaakov to bring wine; rather, Yaakov brought it of his own volition. (Click here and here for Hebrew text.)
It is apparent that the wine did have a positive effect, and in fact helped with the Divine Presence resting on Yitzhak; and without it the blessings would not have been the same.
We learn from this that outside sources are acceptable to be used to help a person feel good. It is also suitable to take appropriate precautions to use these outside substances to help one feel happier. This is why Yaakov erred on the side of caution and added the wine, in addition to the meat, to ensure that Yitzchak’s heart was uplifted; even though Yitzchak was most likely elated to give the blessing to his offspring, which meant that, on his level, he was at least hovering around Divine Inspiration, even without the wine.
A caveat, however; the Orchos Tzadikim (chapter of The Gate of Joy)warns: “There is another kind of confusing joy which beclouds all of the mizvos and causes fear of Hashem to depart from the heart of men – that of the drinkers and revelers at bars. The end of this joy is sorrow, for many ills result from the frivolity of drinking.” Later theOrchos Tzadikim says: “Drinking wine, however, is very good when it is done properly in the manner of the wise, as King Shlomo writes (Mishlei/Proverbs 31:6, 7)… It is further said of wine (Shoftim/ Judges 9:13) that it ‘gladdens G-D and man…’ All of this teaches us the benefits of wine when it is drunk in moderation in the manner of the wise –in which case the mind rules over the wine and not the wine over the mind – who drink at set times with friends and acquaintances and with saintly and the righteous, and not with boors and empty-headed people. For wine will increase the wisdom of the deep…”
Wine when drunken appropriately has an uplifting effect on a person, even one who is holy and already very close to Hashem. It can even tip the scales to allow the Divine Presence to rest on him and inspire everlasting, impacting blessings in a way which would not have been possible without the wine. For this reason the Rabbis felt much gratitude towards wine, and gave it a special blessing, in return for helping the Jewish People receive such lofty blessings.