Small quantities

It's a topic that's difficult for me to tackle, but frankly, I need to start cooking in small quantities when I'm at home. Why? Because if I don't, I'm going to wind up wasting food, and that's not a good way to keep my food shopping under control. Here's a helpful list for me to keep on hand, so that I remind myself of what a reasonably sized portion for one person (for one meal) should be.

1/4 cup of rice

1 potato

1/2 head of cauliflower

1/2 lb of spinach (cooked. Spinach is depressing in how much it cooks down!)

1/2 cup of beans

1 cup of red lentils (they're magic, and finish FAST)

1 cucumber

1 tomato

1 small red onion (or shallot, come to think of it)

1/2 cup of chickpeas, soaked and boiled (for hummus)

Ugh. This is depressing me. What are some tricks you all use to keep quantities small and manageable? I know I need to start doing it, because it's quicker too. 1 cup of rice or 1 cup of beans takes much less time to cook up than 5 cups of the same. Any tips from my lovely readers out there?