Seeking insight into depression/anxiety

Disclaimer: I am not in any way, shape, or form trying to mock or offend anybody suffering from depression/anxiety. Do not accuse me of being ableist; all I seek is insight.

I’ve always considered myself a very rational and optimistic person. I have a hard time understanding why anybody would suffer from depression or anxiety to the extent where it leads to being unable to work, suicidal thoughts, panic attacks etc.

I just can’t wrap my head around how hard it can be to just get up and get over it (sorry if it sounds harsh; perhaps I am too rational). I’ve been through tough situations, yet I have never suffered from depression nor anxiety.

However, I believe that ignorance ought to be countered, which is why I ask you. Why is depression/anxiety so hard to deal with? Looking forward to hearing from you.