There's no point in writing a goal if you're not laser clear on what you want. Goals need to be specific, meaning well defined. Anyone who reads the goal should be able to understand exactly what it is you want.
To prove you met your goal, you'll need to make sure it's measurable. This means you'll need some way to track whether you're on track to achieve your goal.
Why make a goal you can't reach? Goals should always be something that is realistically possible to do; otherwise you'll be too challenged and not want to work on it.
Our focus should be on a measurable outcome.
Be specific. You want to have a start and end time, not something that lingers.