I found you can choose to ignore tasks and they'll come up the following year if they are seasonal or you can just abandon it all together.
Some characters are annoying you go to give them what they requested and they don't take it straight away instead first giving you another one or two extra things to do before accepting what they asked you to do before!
I try not to take on too many at once by not talking to anyone until I've finished the last lot or reading ahead to see who will give me the quests I need to achieve a particular goal like get the barn built! ...cheating a bit I know!!