...in relationship?

I've decided to start with such a serious topic, so I put my glasses on and go further.

There are lots of approaches in studying what is called an ideal relationship.
Certain people consider that the main source of happiness in relations between men and women is just a lot of positive ideas.
Can it be true? Why not.
I think it's not very good when you always say to your partner that everything is bad, the things are getting worse and worse etc...
Sometimes, it is very important to notice some disadvantages of a person you live with - but it won't be very pleasant if you will make accent only on the worst traits of character of a person you are going to share your life with... Simply just because it's not correct. It takes away a lot of forces, a lot of life energy... A lack of optimism can really stuff your head with rubbish which it will be very difficult to get away with time...
You should better combine pros and cons of your cohabitation. The question is only HOW.
It would be great if a couple can clean up the bad sides of life and develop the good ones like an expert...
To my mind, that is really a clue to a happiness.
What do you think about it?
Is the optimism so important for a relationship?

Your smarty Tamara.