I guess all people have feelings like that sometimes but for us, who have depression, these feelings can be overwhelming. I would say they are symptoms of depression. And at the same time giving into them deepens our depression. Please remember that depression is not your 'weakness' or fault. Asking for help and/or understanding is not 'dumping stuff' on people. It's a normal human need because we are not self-sufficient. Were the roles turned, meaning was your wife the one suffering from depression, would you think she's a burden? Would you want her to shut down from you? Probably not, right?
With depression we tend to be so hard on ourselves. Feeling helpless and at the same time remembering all the mistakes we ever made... It's a terrible place to be in. But we are human. We have our flaws. People with depression are no worse or better than any other people. We just need to accept ourselves and try to make most out of the present. Past is gone. Future is uncertain. Here and now we can talk, share and work on our issues. It can be really hard, true. But we can make it. We have to make it, one of the reasons for that is that we will be able to be there for people close to us when THEY need us. People need people. And there is absolutely nothing wrong with that.