How would I go about understanding my insecurities and work on eliminating them or coming to terms with them? I realize that my insecurities negatively affect every relationship that I am currently in and ones that I have lost because of my issues. I don't want to continue to carry them around with me and deposit them on others.
Insecurity or a lack of confidence is just another way of saying you live in fear. Thus, the solution lies in understanding what you fear and dealing with it.
Most fears stem from facing the unknown. It is because we don't know what to expect that our imaginations run wild. We always manage to imagine things to be far worse than reality. Then we lock up in fear of causing our imagined harm or we sabotage our own efforts to keep us from moving into unknown territory. See "Overcoming Fear" for examples in dealing with fears.
Some run from their fears, others mask them with alcohol or drugs, but the solution is to look at what we face and divide them into two categories: those we have control over and those we do not.
"God, grant me the serenity
To accept the things I cannot change,
The courage to change the things I can,
And the wisdom to know the difference."
[from the Serenity Prayer]
When something is in our control, then take action to start the necessary changes. If a boy wants to meet a girl, then he has to take action. He needs to introduce himself and talk to her. He might fear her rejection, but he should understand that her reaction is not in his control. Her acceptance or rejection of him is her choice, not his own. Whatever she chooses doesn't change him.
Most things in life are like that: a mixture of things we can do and things we have no control over. On a job, I have control over how well I perform my duties, but I have no control over whether my efforts will be recognized and rewarded. I can be a valuable employee in my company, but I have no control over the economy or how well the company is being managed (unless I'm the boss). I might be let go for reasons that are completely out of my control. "For this is commendable, if because of conscience toward God one endures grief, suffering wrongfully. For what credit is it if, when you are beaten for your faults, you take it patiently? But when you do good and suffer, if you take it patiently, this is commendable before God" (I Peter 2:19-20). It isn't worth worrying about things I can't control because worrying won't change those things. It isn't worth worrying about things I can change, I should be putting my time in productively improving things instead of worrying over them.
For the things we can't control, we leave them in God's hands. "Let your conduct be without covetousness; be content with such things as you have. For He Himself has said, 'I will never leave you nor forsake you.' So we may boldly say: 'The LORD is my helper; I will not fear. What can man do to me?'" (Hebrews 13:5-6). Sure, there will be hardships and trying times, but whatever I face I know that God is watching and will see that in the long run, things work out for the best.