Trust is sometimes a hard thing for people (perhaps because they don't understand what it means to trust someone). It doesn't mean I trust you to never hurt me or fail me; but it means that when you hurt me or fail me, I will trust that you love me despite the imperfections and weaknesses that I see. I will trust in your motives, I will trust that you are trying to improve and grow in areas. I will trust that you are sorry for hurting me.
I Corinthians 13 mentions that love "believes all things and hopes all things." Can we understand that only perfect people can keep from hurting us or misunderstanding us? When we believe in the goodness and love of someone's heart for us, it doesn't hurt as much when they fail us, say something wrong about us, or get mad at us. This can be true because out of an attitude of trust, we are able to make a case for their love for us, rather than a case against them.
Trust is similar to faith in that our trust isn't tested until the evidence seems to contradict what we believe. Many people hold back trust because they want to be able to trust "safely." I don't believe we should put ourselves in reckless situations by trusting just any body; however, we cannot raise the bar so high that we do not trust anyone. If you have no one whom you trust then you probably need to adjust your perspective of what trust means.
Look at John 2:23,24 - "Now when He was in Jerusalem at the Passover, in the feast day, many believed in His Name, when they saw the miracles which He did. But Jesus did not commit Himself unto them, because He knew all men."
The Greek word for commit means to entrust, especially your well-being.
Like Jesus, I will not entrust my self-identity in your hands, or my source of joy and happiness to you. What you say about me, do or don't do for me will not determine who I think I am. However, I will trust you to love me, lead me, instruct me, or co-labor with me.
Trust is actually a deeply held belief in the good of people, and believing that we are loved, despite any evidence to the contrary. There are some people that we probably cannot trust (because they are abusive, destructive or full of hate), but most people will live up to the trust we place in them. Our belief in them will motivate them to live up to our trust. Even though they fail us, we encourage them to keep trying by believing in what God has placed within them.
The first place to start in increasing trust is with God. Can you trust His goodness and His love for you? Can you abandon yourself to the promises of God? When things go wrong, are you able to say I don't know why this has happened, but I do know God is good and wants only good for me. Therefore I know God is not the problem in this situation.
Determine to trust in people again, trust in their hearts even when they blow it. Take the risk; you will make life-long friends!