By all means, eat as much healthy food as you can afford. But whatever caused your psychiatric problems, it couldn't have been food. Unless you're so poor that you severely malnourished, or you're eating something severely toxic. And even then, lots of places in this world with malnourished populations that are not depressed.

Improving the quality of your life is not just food. It's all the other things that go into it. Like autonomy, sense of security, friends, social status, finances, physical activity levels, etc.

So be sure to look after improving those things too.

And my suggestion for walking a dog, is a simple and practical suggestion for something that will get you both companionship and exercise.

From personal experience, quitting smoking helped with anxiety. That longing feeling for a cigarette was making me anxious, and that feeling would persist even after having one. So quitting was helpful. But again, smoking is not eating.