I choose to go out or to study. I choose to join a gym. I choose to lose weight...
Everything depends on what I choose and what I want. As they say, if there is a will there is always a way. There is nothing such as "I can't do this" or I can't lose weight or stick to this diet. If you really want to, you can do anything. You should have that "will" to find the way.
Similar, I also can choose what I want to feel. I wake up in the morning leaving everything behind and choosing to be okay. I choose to not be depressed. I choose everyday how I want to be this day, and this is how I make my life better. I choose to be happy. I choose not to think about the things that makes me sad and be happy instead.
If I choose to be sad, I'd start thinking about those friends I had that I don't have anymore. I'd think about those who I trusted and betrayed me. I'd think about the things I lost or the things that I could have done better. I'd think about death and fear. I'd think about the defects I have in me, or why did this happen especially to me.
All kinds of depressing thoughts. But what's the point? Being depressed or sad is not gonna help in anything. Nothing will change. And even this could make things worse.
For instance, if I lost someone by a breakup or death, I don't have to mourn about it! These things happen. So if I choose to be sad, I'd start to think about it! I'd think about how it's not gonna be the same anymore. But I can control this. If I choose to be happy, I will try to enjoy what I have. I would move on. I can go out, listen to happy music, do the things I love to do, and keep myself busy in good things. I will not think about how I lost them. I'd think about other stuff and do other things.
I believe we can control our feelings.
We control our mind and it cannot control us.