I'm guessing it's not my donkey that the Lord needs.
As Matthew 21 begins, Jesus sends two of His disciples into a nearby village to locate a donkey and its colt and bring them back to Him. If they're questioned about taking the animals, their answer is to be that the Lord needs them.
What might I have that the Lord needs? Admittedly, the God of the universe doesn't "need" anything from me, but there are things I have that He can use if I will let Him.
Maybe He requires my service in a particular ministry, either at church or in the community. Could it be extra time reading my Bible, more moments of just being still before Him? Perhaps it's a talent I have that I've not been using. Could it be releasing my expectations for what life holds for my children? Or is it a possession or habit that I'm unwilling to give up? Only His Holy Spirit can reveal what God wants from me.
The second question I have to ask myself is whether or not I willingly give it up. It says that the man with the donkey will straightway - as in immediately - send it. If I have something God can use, may I offer it to Him without a fight.
Ultimately, the donkey was used to glorify Christ as He rode the animal into Jerusalem before the multitudes who were crying "Hosanna." So, if I will let God use all of me, it will bring glory to Him.