Sacrifice

The Law of Sacrifice is a great way to get blessings when you need them. Elder Richard G. Scott once explained it with this diagram:

As we strive harder to love and serve and keep the commandments (moving right along the x axis), the Lord blesses us more (moving up along the y axis). When we begin to stretch, to push our limits, to obey and love and serve even when it's hard for us, then the Lord really comes through with blessings.

Fasting is a good example of this. Not only does it make you feel great when done right, but it increases your faith and really makes things happen.