“I am the vine, you are the branches. Whoever remains in me and I in him will bear much fruit, because without me you can do nothing.” John 15:5

Using the image of the vine, the sacraments allow the sap (Christ) to flow into the branches (us), so that they can bear fruit. For example, a baptized person is blessed by God and also receives God’s own divine life as promised. We can say that God’s own life flows in this person’s veins giving life as the vine’s sap flows into the branches to give life.
Sacraments do not change our nature but change our capacities. We become capable of holiness thanks to Christ's grace (the sap).
Look to the saints. They accomplished miracles by letting Christ's work through them

Mother Teresa was a small, weak woman. She wasn’t more intelligent than you or me, she had no specific power besides her faith and trust in God. What she accomplished, though, was totally extraordinary! She founded houses all over the world. Any business man would envy her incredible influence! How could she accomplish so much? She only let Christ’s grace work through her!

When you don't have anything, then you have everything.
The greatest fulfilment is in doing God's Will.
We do not have to do great things, only small things with great love.
We do not have to be extraordinary in any way, I can do what you can't do and you can do what I can't do. Together we can do something beautiful for God. We can be the little pencils in the Hand of God. Mother Teresa (emphasis added)