So we see that they were not able to enter [into His rest], because of their unwillingness to adhere to and trust in and rely on God, unbelief had shut them out.
(Hebrews 3:19, Amplified Bible)

You have a free will, you can choose to receive your blessings from the Lord Jesus Christ or reject them.  Either way you must open the door of your heart through a total trust in Him and His Word to let His power flow though you.  Or you can keep the door closed to Him though unbelief or a lack of trust in Him.  Matthew 13:58 states, “Now He did not do many mighty works there because of their unbelief.”

When you trust Him you give Him a legal right to intervene on your behalf in your life.  That is why we pray.  When you pray you are opening the door to your heart and asking Him to intervene in your situation or desires.  The Lord Jesus Christ’s greatest desire for your life is to have a full time relationship in your heart with Him.  When you abide and live in Him, His life, love and power will flow through you!

Delight yourself also in the LORD, And He shall give you the desires of your heart. Commit your way to the LORD, Trust also in Him, And He shall bring it to pass.
(Psalm 37:4-5)
If you live in Me [abide vitally united to Me] and My words remain in you and continue to live in your hearts, ask whatever you will, and it shall be done for you.)
(John 15:7, Amplified Bible)
Jesus said to him, “If you can believe, all things are possible to him who believes
(Mark 9:23)
“I am the vine, you are the branches. He who abides in Me, and I in him, bears much fruit; for without Me you can do nothing.
(John 15:5)
So Jesus said to them, “Because of your unbelief; for assuredly, I say to you, if you have faith as a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you.
(Matthew 17:20)
So we see that they could not enter in because of unbelief.
(Hebrews 3:19)