When To Say Its Enough

You know at time when we earn money and lets say we hit our 1st mill and you will think 'hey I have hit my 1st mill, so why not the 2nd mill?' I guess we as humans (I admit too) that we need to know when to say enough is enough. I will give you guys some examples of my own life which is like below.

1. Want to buy other guitars and guitar effects when I have 2 guitars (not pro, but want to be at a level of my own )
   
2. Want to buy car when my current car is still ok, but still want to buy car (greed i guess)
3. Want to earn my 1st mill then my 2nd and 3rd (not my dream at all, just example)
4. Want to have something which others have (can be anything).

We as humans we are greedy. we don't really know when to stop at times and we wish that we will be able to earn more than others, be better than others and etc etc. There is no wrong to this but the thing I want to point out is we got to be happy with what we have currently and slowly move on and not move on with a snap of fingers and everything we will have. I guess 1st step is to be thankful with what we have as others might not have what they really need.