says motherhood has given her life a purpose.The 'If It Makes You Happy' singer, who adopted nine-month-old son Wyatt last year, is enjoying every moment of being a parent and the rewards it brings.The 45-year-old star - who has successfully battled breast cancer - said: "Wyatt has changed everything for me, not only in how I look at my life, but right down to my sleep patterns! It's been a wonderful experience having this little joyful, innocent spirit around. He's rendered me fearless and also given me a sense of urgency about what I want to do with my life."Sheryl, who split from champion cyclist Lance Armstrong in 2006, adopted Wyatt alone and is grateful for the support her family has given her.She said: "I don't think I had any expectations about being a single mother, but I've had my family around a lot, so he's not being entirely raised by a single parent. Whether it's been easy or hard, it's been a lot of fun."