Giving and receiving gifts is often much more complicated than exchanging items from Amazon's Deal of the Day. The meaning we ascribe to both the exchange and the gifts themselves makes the difference. The "who" and the "what" of this ritual usually come into play, as your comments suggest. Sit-coms have lived off of these interactions for decades.
"She must like him a lot more than me. He gets an iPhone and I get a potato." Even receiving a "nice" gift can be stressful for many people, reminding us of we don't have, and implicitly acknowledging that other people know this as well, for example. There's also the matter of not feeling worthy, for some people, or feeling entitled to be given something more or better for others. The problem of giving a gift as a kind of bribe sometimes comes into play, and is particularly troublesome when the receiver knows that this is what's going on. "I do something for you, and you do something for me." Or giving a gift in place of loving kindness or genuine affection. There are so many different scenarios that it would take us a very long time to list them.
As for the rest of it, I agree with those who've recommended that you have a workable plan going in and that you stick with it. We cannot account for every variable in advance of any emotionall-charged situation, but it's always much better to be prepared for predictable circumstances than otherwise.
By itself, knowing never prevented anyone from picking up a drink. I know you know this, but no matter what happens or what you're feeling at any given moment, the worst thing that you can do is to drink it all away.