A "weight" for the tasks and its reflection on Calendar & Graph.
To implement "weight" or "priority" for the tasks, as not all task are worth of equal efforts. 10 push-ups are not equal to 4 hours of studying. This should be also reflected on the graph(less important tasks are not lovering the line so hard) and calendar(less important tasks are not coloring the day with red so strong). Just for myself I'm using colors: (i.e red for important tasks, yellow - for not so important an so on.) But it would be nice to see it visually as well(cal&graph)
As variant to the weight - obligatory/not obligatory task.
Taks 1(obligatory) - Go to sleep til 24:00
Task 2 (not obligatory) - stretching