Nowhere in Jesus' teaching on prayer does He place any conditions for prayer to succeed. On the contrary, His very positive framing of the words in His teaching tells us that prayer never fails. It is "always" responded to "Ask, and it will be given to you... the one who knocks will always have the door opened to him." (Mt. 7:7-8).
The prayer Esther offered has some of the best characteristics of prayer. Her prayer was said in a time of desperation, for her life was at stake. Firstly, she acknowledged God's supremacy over all in her address to Him. Secondly, she was honest with God - she opened to Him the challenging situation she was in. She could have been killed for even daring to approach the King. She was absolutely alone. The survival of the whole Jewish people whom God had chosen to be His own depended on her. In reminding Him of His unique relationship to her people, she was humble, admitting that she was helpless and afraid by herself alone, hence her prayer for courage in facing the danger she was putting herself in.
Analysing Esther's prayer, we learn from it what Jesus taught His disciples. Esther trusted in God's unconditional love for His people, the love that Jesus spoke of when He compared God favourably to a loving Father who would never refuse a sincere prayer and with no conditions attached.
Lord, You put no conditions to our prayer, so let us trust You totally and honestly when we pray. Amen.