Hello GoannaLost, can we offer you a warm welcome to the site and it's always great to have newcomers post a thread, because all of us here have been through our own type of depression and know hat it's not easy, but well done.
The Smiling mind may or may not be suitable, it all depends on whether it's something you want to believe can work for you, I feel the same as you, whereas others have great benefit from it, but because you don't doesn't make you any less of a person at all, all it indicates is that there is another way to help you overcome this feeling.
When someone tells to 'get over it', well it's certainly not that simple and unfortunately by saying this only creates a worse problem because you don't have the support you expected from them and are afraid to show any discomfort that anxiety and/or depression cause, and this differs from person to person but still makes you feel lousy, I'm sorry this has been the case.
If these 'awful thoughts' are recurring and may happen for some particular reason then they could be 'intrusive thoughts', and I can say this because I had anxiety and had these thoughts which were rather frightening and certainly unwanted as I suffer from OCD caused by anxiety.
We'd like to hear back from you and your thoughts, only if you want to.