Prayers concerning God's Will cannot be prayed with "if it be thy will", because His will is known and the "if" puts doubt or unbelief in our request.

"If it be thy will" is only appropriate for prayers of dedication or consecration where His will isn't known.

It is important to pray in faith when God's will is known. Prayers for  forgiveness, salvation, healing, safety and protection are all known blessings in His will.

Faith will always praise and worship God before, during and after praying what is His will. This is done before we even see the answer to our prayers because we know He answers us.