How do I convince my parents that I am not a failure?

Its great to have a bond with your parents but what is it that has you so fragile? Your going to have to stand on your own two feet sometime and make decisions in your ife that your parents may not always like. To prove to them you can succeed sounds like you need to bring your grade up for their peace of mind. If you know where you went wrong and have the opportunity to correct it-do it. If you truly can't you need to be honest with them and yourself. Manage your own cellphone plan and you won't have to worry that they reduced your texting or whatever. Pull your bootstraps up!