The only time I've set daily goals is when I've participated in a book in month. Then I knew how many words I wanted to reach by the end of the month and divided that number by the number of days in the month.
Next year, I am considering setting daily writing goals. I think I'll get more writing produced, which I hope means more completed projects.
There are a few ways to set daily goals, word count, pages completed or time spent.
Setting a word count daily goal appeals to me more than trying to crank out x number of pages or allotting myself two hours and producing very few words. However, I am willing to try the other two options, who knows they may work better for me, especially with a day job.
Goal setting is about trial and error, so don't get down in the dumps if you set a word count goal of 1000 words per day and end up only getting 700 words per day...that's still pretty good!