This information is from personal experience (I recently starting to obsessively dream on my desires, which caused me to go into a downward spiral):
When you are trying to manifest, from my experience, it is not ideal to try and dream all the time. Dream big and have faith it is already here 100%.
When you do this technique so, do only once. Get in a meditative and relaxed state. Visualize what you want in first person using all the appropriate senses. Make sure it's in color and it's a movie, not a picture. Do this for 68 seconds then be grateful that it's already here.
If a thought about of your dream comes up again, it is ok. You can just quickly be grateful and know that it's already here. Be wary if you start to dwell on it. Get a image on your phone or computer if you feel the need to (it can help initatite the process of dreaming).
If you wish to do this everyday, do so at the end of a the day for no more than 20 minutes. Sleeping can help you manifest your dreams. Then for 10 minutes be grateful for what you already have (your current physcial being and possessions) . If you are calm, go to sleep, if not, make sure you are calm.
However, don't get obsessed and start dreaming all the time, the bliss of the present moment and now will escape you. You are being sent messages all the time from God on how to get to on your life purpose (which is a journey that brings bliss and fulfillment) and these messages will also escape you. You may start to not listen to your gut and not take actions. You may become maniacal or insane.
Even if you did get all you want, you would still suffering, because the state of wanting is a endless chase of suffering. You would just want something else after you got what you initially wanted. Feeling good while dwelling on dreams is a drug that can suck you in, be careful not to be hypnotized by it.
The truth is you have all that you could every desire now and that your true being right now is perfection. What you desire it is not outside of you.
The origin of the word desire means to crave something, and if you are craving something, you aren't thinking of having it now and it leads to suffering. You think what you want is outside of yourself and that you have to chase endlessly to find it, and you are never content in now. You can have the feeling of having what you desire now by knowing you are a perfect being and immersing yourself in the present moment deeply. Think of the most blissful moments of your life, you weren't dreaming, you were enjoying the moment of now! You had little to no thoughts, you fully immersed!
The origin of the word want means to be lacking, If you want something, you are saying to yourself you don't already have it. If you had a computer you wouldn't say I want a computer, because you already have it. If you are thinking and feeling you are lacking and continue to think so, no riches or fulfilled desire will content you.
Knowing the etymology (origin) of words helps you create a live of bliss and freedom. People speak words that they don't know the origins of and this causes them to be "Hung by the Tongue". This is what makes someone a wizard, but that is for another time.
Have mild preferences rather than desires and wants. Dream but don't live in a dream world.
The movie clip is was mentioned in an excellent book called Happy Pocket Full of Money and illustrates some of what I am saying here: