When things get busy, I make sure to calendar "White Space". White Space is time that is blocked out without obligations. Today, a Saturday, is one of those days for me and it's allowing me to catch up on all of those miscellaneous types of items that pop up in life which you often never get to.
If you find yourself with piles of different things to do that just don't get done, block out on your calendar some of this White Space. If anyone wants to make plans or anything pops up, don't fret. If you have another slot of time nearby, just move it over! If you don't have other time available, however, I recommend sticking to your guns.
White Space is similar to the "Pay Yourself First" concept of personal financing, but with time instead of money. Pay Yourself First refers to investing in your savings, personal investments etc. White Space is just like this, in that the time that you've blocked out is allocated to serving you!