One trend I've noticed with git users is a habit to create a lot of branch and merge activity. The oft-repeated mantra is "branching is (easy/cheap/safe) in git so I do it a lot". When working on an agile project though, this behavior can cause serious problems. To illustrate the point, compare american football to soccer: American football has highly specialized players and positions as well as a variety of tightly choreographed set pieces.
In contrast, soccer has a much lesser degree of specialization, and while there are some set pieces that are choreographed, the majority of the game is spent reacting to the situation as it evolves. Traditional development methodologies are like american football: They divide the work up among highly specialized players and then try to replay an intricate set of movements to make the play "work". Agile methodologies are more like soccer (or to a lesser degree rugby) in that the advantage doesn't come from following the choreography (or even rehearsing it), but from reacting to the current situation on the field and having visibility and vision as to the current state of the field. When teams start creating a lot of branches and working in isolation for large periods of time (relative to release frequency), that means they are often making assumptions about how the plan is supposed to work.
Unless this has been worked out well in advance, it often leads to a "massive catastrophic merge" when everybody tries to come back together. To maintain an agile development process, it's important to react to interdependent changes as early as possible and reenforce the notion of a team of generalists who must react and move based on the current situation, NOT by following a plan that was written months before. So, if you're on an agile team of 5 and each of you are working on multiple independent branches and not sharing them on a daily basis, you're probably trying to play american football. Instead of developing vision and dealing with the ebb and flow of the game as it unfolds, you're trying to rehearse what you think your role in the project is supposed to be so that you can execute your portion perfectly at the appropriate time.