Make a day plan by adding your To Dos to a calendar along side your appointments. This will give you an idea if you have enough hours in the day to get everything done.
Keep long term activities separate from you day plan and bring them onto your day plan as small tasks. An unspecific task can detail your whole day as it stares back at you. You have a bigger plan for long term activities somewhere, even if it is just inside your head. When the time comes, create discreet tasks that can be completed in a short amount of time and put them in your calendar.