That's incredibly reductive. I'm sure some people's depression can boil down to a matter of perspective, but it's naive to extrapolate that to everyone with depression.

I'm incredibly optimistic and am content with my position in life. My default state is being mindful of the present and I don't think about things too far into the future. I very rarely ever feel stressed out over things in life.

However, none of that changes the fact that I feel completely empty and find no joy in things. Interests are nearly non-existent, emotions dialed to 1, and the only thing I'm motivated to do is lay in bed staring at the ceiling... unless I'm on sertraline.

Admittedly that's just anecdotal, but I worked in a clinical neuroscience lab researching treatments for severe treatment-resistant depression (read: people who tried so many options including CBT that they even tried electroshock therapy). The only thing that helped those subjects was a regimen of personalized neuroimaging-guided transcranial magnetic stimulation for 10 minutes every hour for 10 hours every day for a week. Even then, it wasn't permanent. Some saw improvement for months, others only weeks.

For some people, it's not just a matter of "perspective".