How can I stop having negative thoughts and be happy even though I’m not happy?
The only thing guaranteed is pain.
One of the cruelest things in life is the false belief that life shouldn't be painful. In reality, it's quite the opposite. Life is full of pain, both good and bad. Good pain is the pain we endure on the road to our highest values. Bad pain then is the pain we experience when we avoid what matters to us because of fear or anxiety. Then when we feel shame or guilt, that is when we are in a bad pain situation. So, in your situation, what sort of pain are you in?
The way you speak, it is as though you are a victim of circumstance. Life beating you down and no opportunities at work, is this what you want to teach your daughter? Do you want to model that you should only be in good spirits when fate or luck goes your way? Now, I know our language to a three year old seems insignificant, but you are acting as though what you believe to be true. Not just your language, but your body language, your choices, motivation, spirits and how much you engage in play. You become what you think. Your thoughts determine how you view life and it will be noticed by your daughter.
Here's the good pain, to notice when you have those familiar negative thoughts and instead of indulging them you choose to see some alternative, something good in it all. You look for the good to start the habit of looking for the good. If you find the pain helpful in life because of the lessons it teaches you or the coping you have to practice, you can change your entire life. Honestly, look for the good in every situation and you will see good. Think about how going to the gym strengthens muscles. For you, working your brain to see how you benefit from every situation is the new exercise to then see the benefit of experience. From that perspective you will live differently and model endurance in even the toughest situations.
When you experience situations in life that you allow to wear you down (choice) you can break the habit and see the positive in it (choice). This is all your choice and breaking habits is painful, but it's the pain on the road to what matters most in your life. You want to model good behaviors, it's not about circumstance, it's about what you choose to see in any situation. Again, it's all pain, life is full of it (accept it). So, instead of avoiding pain by putting responsibility on to circumstance and off of you, own your choice in life and accept life as it is. Imagine, you are in the same situation but view it as a learning opportunity, how great life can be in any circumstance. Don't believe the thought that your life will only be better when you get the opportunity at work or get a win at life. That belief is a cancer and shows your powerlessness. You give up your power when you think it's dependent on life circumstance.
Take your power back, own your choices, practice seeing the good in any situation, and you will model the resistance you want to see in your daughter as inevitable pains will come her way in life as well.