Also Serves Who Stands and Waits...
Ever entered a writing contest where the results aren't known for months? Sent off a query that takes ages for a response? Instead of biting your nails , use the in between 'waiting' time constructively.
Presume the worst case scenario and opt for responding to that situation i.e.assume you might not hear from a particular publisher, so line up your query letters for others and if you're waiting for a 'results posted' date, when that date comes and goes and you get the 'bad news' i.e. manuscript not accepted, send a new batch out ---keep the continuum going and yourself motivated. Always have something 'on the go' so you don't get bored with the process.
Some will send out a batch of the same material whether waiting or not for a response . In that case , just make sure if you hit 'pay dirt' with one publisher that you inform ALL the others that you're 'yanking' that manuscript from their consideration. Try not to be smug about it if you grasped the brass ring---burning bridges is never a good thing in any pursuit.