Why I have been dreaming of making my own compost?

Compost feeds animals that live in soil. For example, earthworms. They reproduce more and move around in the soil. They create pores for holding moisture and air and make your soil loamy for plants. That's way to save water in the garden.  

Moreover, when earthworms digest organic matter in compost for food, their casting will stick the soil particles (both finer clay and coarser sand) together to the compost, forming a soil crumb structure. 

Soil particles like sand, silt and clay will stick to the humus in finished compost, forming soil crumb aggregates. Soil crumb structure improve any type of soil.
How Compost amend garden soil?

All About Water and Oxygen

The crumbs create countless micro-spaces in the soil where oxygen and water are. Oxygen is crucial to root growth and function. Therefore, compost changes your soil no matter what type of soil you have.  Compost also acts as a pH buffer if your plants are sensitive to soil pH. 

Between soil crumb aggregates, there are pores to hold water and air. Plants roots need air because they can't photosynthesize. The need oxygen to respire to produce ATP energy.
soil crumb structure creates more spaces for storing water and air

Compost Amended Soil Naturally

The commercial “organic fertilizer” you bought from the garden center is expensive and bulky. It won’t form soil crumb because it has been dried and has lost its structure. It provides no food for earthworms. It has some nitrogen for your plants but you need to add significant amounts, which can make growing your own organic vegetables difficult and expensive.

If you buy compost from a farm, you never know what the ingredients are. How were they made? Compost may contain pathogens or weed seeds if it didn’t reach 60~70 degrees Celsius during its production. You only want to apply safe compost. NPK also varies in different batches. You never know unless you test it. 

Remember, no fertilizer can make up for poor soil structure. Too much mineral fertilizer will even kill soil organisms, such as earthworms and bacteria. Therefore, a healthy and sustainable garden always starts from composting.