It has been proven some time ago that our brains are neuroplastic, which means we just get used to state in which we spend the most time and then this state is our primary state of mind. Of course it's entirely up to you -
how you react on certain circumstances but if you already fall into abyss of sarrow and cannot see any way out, then instant contradiction is no use. In my opinion it would be just lying to ourselves (and we are actually aware if it) and we perfectly know that the situation is much much worse. That can lead to inner dissonance or even inner fight which just will leave us wasted and completely out of power, so the negative attitude gots straight way to overwhelm us. Sometimes it's not easy to change attitude but in my opinion best thing you can do is not to negate but rather accept thing as they are first. So what if I'm actually being in prison - thinking "but I still got my free will", "I am free man, I can do whatever I want" doesn't change the fact that I'm prisoned. Istead if I would be like "OK. I'm in prison and I can't get out where I please but I can still do a lot of things inside the prison and get through this experience. Maybe it's good time to change some of my life priorities and prepare better to live as a free man again? If I already found myself in such a situation what can I learn from it?
Negation and hiding negative stuff under the carpet won't help. Things will get even worse when after some time you'll realise that you've been lying to yourself about this whole time. All humans can adapt to almost every condiotion but it takes some effort and time. Of course you can still change your attitude and work towards changing the situation on the better, but without acceptance you'll be in constant fight with yourself - that will only be restraining you. So let go, accept the negatives, look toward the bright sides and then work on them.