If you think there is even a remote possibility that you might bake a cake on any given day this is my advice: take a pound of butter out of the fridge as soon as you wake up and put it on the counter. You should also take out the other cold ingredients, like eggs, sour cream or milk. (Although I must say that if I even think I might bake a cake, the odds are more or less 85% that I will and this may not be true for everyone.)
The butter and eggs emerge from the refrigerator dense, fatty and cold. You won’t be able to beat any air into a batter composed of cold ingredients. If you have had the forethought to take the butter out of the fridge in the morning and it is perfectly soft, watching it beaten into a pale fluffy mass with the sugar is very satisfying. The eggs too, at room temperature, will balloon when beaten, doubling in volume, becoming ethereal and nearly white. Light batter makes a light cake. The butter and eggs provide moisture and structure.
I baked cakes for a really really long time before I became a believer in properly softened butter and understood the value of warming up the cold ingredients. The little extra effort of pulling them out of the fridge in the morning makes all the difference.
I’ve been thinking about cake daily because the season of birthdays for our family starts on February 7th and doesn’t end until May 3rd. I have to bake a birthday cake about every 3 weeks (and those are in addition to any cake I might just make on a whim) and several batches of cupcakes besides. I don’t like to make the same cake twice. That adds up to a lot of cakes.