That is going to be too hot for ideal flavor. Fermentation temperature is usually at least 2 degrees hotter than ambient temp. If your house is 78 degrees during the day, then your beer is probably fermenting at 80 or 81 degrees. You will still make beer, but it will not be as good as it could be, and will likely have some "off flavors" due to the high temps. I suggest researching "swamp cooler" on this site for a cheap (nearly free!) way to manage fermentation temperatures.
Essentially, get a container that is waterproof, and large enough to put your fermentation bucket or carboy inside. Fill the larger container with water to roughly the same level as the beer in the fermenter. Freeze a couple of 2 liter soda bottles full of water. Place one frozen bottle in the water each morning, and swap out with the melted ice bottle with the other frozen one at dinner time each evening. Swap again the next morning, and so on... This will usually drop fermentation temperatures several degrees, and maintaining a steady 65 degrees is fairly easy with this method. This way you can keep the temps ideal without spending a bunch of money, or a ton of effort. Temperature control is probably the single biggest thing you can do as a homebrewer to make the best quality beer. You will be surprised what a difference it makes.
