Dream about being happy with someone will make you happier ever. But do you think having any dream make you a happier, more fulfilled person overall? My answer is yes, dreaming can make you the most happiest person in the world except you dreams are nightmare. Every good thing starts with a dream even though if you imagine it, or feel it while sleeping. If you are tend to be happy your neuron will work for you, and they will let you meet with your happy dreams which actually makes you happy and those dreams are always seems like real. 

But if you are afraid to have dreams, or you have insomnia, nightmare problem, then probably having a happy dream could be harder for you. But don't be hopeless, in these case its also be possible to become happy.
If you know what makes you happy it will be so easy to become a happy person. be honest to yourself and don't think that your preferences are good or bad - just find out what you like and what is important for you.

You have to be just as intentional in growing and fostering personal satisfaction as you are in growing your businesses, and that means you must dream.

Emotions are often an integral part of dreams.

These emotions or emotional states are not disguised as in real life. This means they are reflections of individual’s true feelings in life. However, happiness is one feeling or emotional state that is often compensatory in nature and you are sad or distressed in real life when you dream of happiness.

Dreaming can help you be more productive

Whether you are student, employee, entrepreneur, housewife or doing anything else, dreaming can help you be more productive. Wait, what? more productive means you are more successful, and success brings you happiness.

Think about it this way: When we dream, we grow, and growth happens when we leave what we know and move into what we don’t know. Would your 18-year-old self be able to do what you’re doing now? Probably not. That’s because in the intermittent years, you’ve had many new experiences and grown as a person.

When you continue to dream—and hence, grow—so does your capacity as a person, expanding your comfort zone and making it easier to do things you once found challenging.
 
If you feel like you're making progress in your life, You can work better and for more hours. When you have a greater purpose in life, you’ll be more engaged, and engagement directly impacts businesses with greater profitability, customer satisfaction and productivity. And when you think about it, dreaming is just a higher form of engagement.

If you are doing something in life that your heart is not comfortable with, you become unhappy and sorry without you knowing the reason for your unhappiness. If you do not follow the commands of the almighty or remain indifferent towards these commands, you tend to see yourself happy in your dreams. If you face hardships in life that make you cry and you remain stressed out, you are likely to see dreams in which you are happy.

Despite happiness in dreams reflecting sorrow in real life, you are happy when you are happy in your dreams under the condition that this happiness is for your friend or relative. This is the only time when your happiness in dreams extends to your real life.
 
It’s easy to get into a space where you feel your dreams take a back seat to the needs or dreams of others in your life, or that your dreams are dictated by circumstances beyond your control.

Dreaming isn’t about whether you can or can’t

The No. 1 thing that prevents people from getting started, let alone moving forward, is their willingness to commit. Achieving a dream requires consistent and committed effort, and staying committed in the face of adversity is extremely difficult.

Original meaning of Happiness and Dreams

Happiness is one emotional state that does not spill into real life when you find yourself happy in your dreams. In fact, it is on the contrary and you are sad or stressed out in real life when you see yourself happy in your dreams. If you are feeling happy in your dream, it means that you are sad, crying, or full of sorrow in your real life. It is your brain that tries to compensate for sadness in real life by conjuring up happy dreams.

You have this opportunity, no matter where you are in your life, to figure out what gives you butterflies, what makes you nervous, what would take a little bit of a miracle to happen, and then decide to step in that direction with boldness and fearlessness.

Most Common Happy Dreams:

• To Smile while Dreaming: This is one of the most common happy dreams. We don’t have a reason why we were smiling in dreams, but quite often we wake up while smiling. It is a sign of being happy. Happiness is a state of mind and you need to remain happy no matter what the situation is. 
• A Happy Baby: If you saw a happy baby in dream, it is a sign about the happiness of your children. These dreams indicate that you must spend time with your children as they feel happy with you being around. Moreover, the dream is a reflection of your inner feelings and it takes you to the flashback of your happy childhood days. 
• Laughing Loudly: To dream that you were laughing loudly indicates a sign of satisfaction. You will feel satisfied about a mission accomplished. According to the myths, laughing in dream is a sign of sorrows in reality.
  

Definitely imagining or dreaming about a good thought always gives happiness. But I would say, Happiness is everywhere, all you need to believe that it exists everywhere in reality. Yeah believing is the most important point out here. Life becomes whatever we  believe in.

Walt Disney once quoted;

"If you can imagine it you can make it real" 

Another good inspiring words I can remember is  

"Dreams lead to thoughts thoughts lead to action action leads to realization" quoted by Abdul Kalam (4th Indian president and missile man of India).

So equating both the statements I hereby disprove the statement made in the question you can dream of happiness but if you want to make it real or not it is up-to you.