Why is it that many people advise investors to set specific goals before investing and what would they like to achieve? (E.g. to buy a house, to fund children’s education, etc.)? What if I don’t care?

You may not see the need to set specific goals for different purposes now because you might not have that commitment yet. While for others, they need a specific amount of money to fund varying purposes like housing, kids, wedding etc, that's why they set and amount and timeline for themselves so that they can review regularly if they are in track.

If there's no goal, how do you know you are performing well? How do you know you will be happy with this amount of money after investing for a few years? It may be easy to say just continue investing and earn alot of money forever, but you may realise your rate of returns are not able to sustain the increasing cost or the increasing commitments that you may undertake in the future, so a goal allows you to track where you are at and review your methods.

I think I know where you are coming from. I also do not really have very specific goals. I find it no point to track long or short term goals, against any index or targets.

These goals can indeed be stressful. So what if we hit our goal of achieving 10%? What if we miss our goal? Do we get more aggressive and aim for even higher returns?

What I actually focus on now is how do I perform for the year? Did I make any mistake for the year? How can I improve myself?