Regardless of the health condition you have, the blood pressure of any person is not constant but suffers many normal variations during the day, but always measured at rest.
The figures follow a rhythm blood pressure over 24 hours, which is reproduced from one day to another and is called nictemeral rhythm of blood pressure, so that the pressure values are higher during the day and are reduced during sleep.
The daily requirement of salt are about half a gram a day (half teaspoon), but in a normal Western diet is consumed eight times that amount, not only in salt shaker, but also in cheese, cold cuts, condiments, soups envelope etc. Excessive salt in diet causes fluid retention and increased BP. To lower the TA, the first step is to reduce total salt intake (including that contained in the bread, broth concentrates, prepared foods, etc..) To a smaller amount of a teaspoon a day. Sodium is not only salt but also in monosodium glutamate, yeast, etc, so you have to read labels of packaged products to make a strict low sodium diet.