Helping myself and My family.

The lord gave me a second chance to turn my face to him. I made the decision to know him and follow him. am 28. Immediately afterwards though, i found out that its not easy staying along the track while living in the same world i am living. These past few months have been in the most challenging period of my life so far, it still is. I have a young sister fighting schizophrenia and a mother doing her best to remain strong. I keep praying to God to end my sister's suffering and bring her heart to him and to let my mother follow him only. But sometimes, i find myself feeling like a liar and deceiving God praying for my family, when i myself feel my faith shaking and losing hope. And after so many years of neglecting my sister, i can not seem to be able to gain her trust and love to be able to talk to her about Christ. How does a very young Christian remain strong and faithful with so much challenge? How do i know yet fully knowing the words of the lord keep myself and my family together in christ? How does one keep promise a promise made to God? I need to know how to help my sister?