Remain in me

Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.
John 15:4 KJV

Grafting is an horticultural technique whereby tissues of plants are joined so as to continue their growth together. There are great benefits for the plant the scion that's growing on another plant called the rootstock. It was an agro economy then and the people understood what Jesus was teaching because a lot of people where farmers or agriculturists.

A branch cannot bear fruits by itself unless it remains attached to the tree. So a lot of people try to  ear fruits as branches and then get discouraged or disappointed when they discover that they are not bearing fruits. Abide in the vine and get nutrients from there to grow. Stay connected to Jesus and his teachings.