Eph6:18 And pray in the Spirit on all occasions with ALL KINDS OF PRAYERS and requests...NIV
Mark11:24 Therefore I say unto you, What things soever ye desire, when ye pray, believe that ye receive them, and ye shall have them.
The type of prayer Jesus talked about in Mk11:24 is called the prayer of faith. In this type of prayer, you don't repeat the same prayer twice, once you finish praying, you believe that you receive and start thanking God for answers. This type of prayer is not a prayer of 'God will do it' but rather, 'God has done it'.
This type of prayer is used to change situations and circumstances. It is for personal use because it is your faith that determines the answer. You can't pray the prayer of faith for someone else except the person is a baby Christian and hasn't learnt how to walk in faith. In this type of prayer, you don't say 'If it is thy will' because the will of God is known already via his word.
You don't pray for healing and say 'Lord If it be thy will, heal me'. That's doubt at work because it is God's will to heal you you as revealed in 1Pet2:24, Matt18:17. You only use the phrase 'If it be thy will', when you don't know the will of God on a matter. As long as you know God's will, just pray the prayer of faith, believe you receive when you pray and start thanking God and making positive confessions, you shall have it.
Look for a need in your life, pray about it according to Mk11:24, believe it is done and start thanking God thereafter.