"For ye are yet carnal: for whereas there is among you envying, and strife, and divisions, are ye not carnal, and walk as men?" - 1 Corinthians 3:3
Envy and jealousy cause us to strive after things that Heavenly Father will give us in His timing, if it is His will that we have them. A jealous, envious heart in no way blesses. The negativity spills out over others that He means to bless through us.
We need to be happy with what Heavenly Father has given us. We need to trust Him that if we are supposed to have more, He will give it to us when He knows we are able to handle it. We also need to be eternally grateful for all that he has blessed us with.
When I served as the 1st counselor in the Relief Society Presidency the 2nd counselor shared with us that when she prayed she always expressed her gratitude. She explained that when she first started expressing her gratitude in pray it was a little foreign because she was taught to pray and ask for things. I decided at that time I needed to express my gratitude more. It has been many years since that time and I continue to express my gratitude. As a result I have been able to recognize the great wealth and abundance my family and I have. Asking for more or wanting more is not a focus.
But you may feel that the devil is keeping you from being blessed. Look at it this way. If you are doing what Heavenly Father wants you to do, and your heart is right, no man on earth or devil in hell can keep you from having what Heavenly Father wants you to have.
Many times, blaming everything on the devil is just an excuse not to grow up. It is an excuse not to develop personal character and let Heavenly Father do the work on the inside of us that He wants to do. Instead of focusing on the works of the enemy, we need to keep our eyes on Heavenly Father and let Him have His way in our lives.