Don’t beat yourself up about this. It doesn’t matter how good life is, mental health doesn’t discriminate. Maybe therapy and talking with a psychiatrist will help?

Mental health issues often spring from physical, not psychological causes. Your brain chemistry gets out of whack for whatever person, and suddenly you're thinking and behaving very differently. Depression is one way this can manifest; mania is too, and mania can be devastating in its own right. Adult Attention Deficit Disorder is yet another chemically/physically driven state, and while it's popular to believe it's over-diagnosed and over-prescribed, it's very real for a lot of people. Anyway, the point is, it's a medical condition. If you cut your hand open, and the wound wasn't closing correctly, and it was getting puffy and red, you'd go to a doctor, and (presumably) not feel any shame about it. The way your brain is functioning is the same thing; the only difference is, you can't see it with your bare eyes (you often CAN see changes in the brain using imaging technology like MRIs). It's a medical problem; if it's persists, see a doctor about it-- and don't feel badly about it if you do!