It's human nature for us to desire a shoulder to lean on. But when that shoulder belongs to another human being, we are bound to be disappointed. The Bible teaches that people have their limitations. Even on their best days, our friends and loved ones can let us down. However, that's exactly how God intended it to be. He wants to be our only, never-ending help in times of need.
Philippians 4:19 promises that "God will use his wonderful riches in Christ Jesus to give you everything you need." This means that when you need a shoulder to lean on, you can use His. People may be eager to help, but only God will reliably show up to strengthen us every time. Our Heavenly Father has given us the need to rely on someone. We just have to remember that the "someone" is Him.
In the Garden of Gethsemane – while He was struggling with the burdensome call on His life – Jesus knew that His disciples loved Him. However, He also knew that only God could help Him in His darkest hour. After crying out to God in solitude, Jesus said to Peter, "Can't you stick it out with me a single hour? Stay alert; be in prayer […] There is a part of you that is eager, ready for anything in God. But there's another part that's as lazy as an old dog sleeping by the fire" (Matthew 26:41, The Message Bible).
Like Jesus, we must always be aware of what role people play in our lives; versus what role God plays.