For example, Sylphs (Air) can whip Salamanders (Fire) into a frenzy. Gnomes (Earth) and Ondines (Water) can aid in putting out those flames. Etc etc.
This is applicable to our everyday mundane life as well. If some Ondines (Water) are having some fun at your expense, you may experience numerous dreams of flooding, losing all you belongings to such floods or you may become ill with a sinus infection which also can be a sign of overactive, mischievious Ondines. Although Water has the potential to put out Fire, Fire also causes Water to evaporate so to clear up such a sinus problem, perhaps you would call on the Salamanders (Fire).
This is just one example of problems you can encounter if you do not treat the Elementals as they should be treated.
The easiest way to avoid such problems? Show respect when you work with them and offer them gifts of thanks when appropriate.