Typically when I cook, I only need a small spoon full of tomato paste...and end up having lots left over! I've tried saving it in my fridge, but I forget about it, or don't use it in time and I end up having to throw it out.
A tip I learned is this:
If you have leftover tomato paste, chicken stock, etc. simply freeze it in ice cube trays, take them out once hardened, put in a ziplock, and you have small servings whenever needed! It's a great way to save.
Happy savings to you!