For many, the problem is that manifesting as they see it involves actually making the desired outcome happen after projecting yourself into the future, Well, one has no control over what happens and so the likelihood of frustration remains great.
In an earlier post, "Manifestation - DANGER, DANGER!" I wrote how this form of manifestation is antithetical to the teachings of the Buddha, antithetical to being present.
Another type of manifesting that i've been exposed to is about creating a feeling and belief that something is going to happen, not making it happen. Here you are still in the present, but the problem is that the ego-mind's negative reaction based on one's life experiences is so strong, that it typically overwhelms our attempt at maintaining a positive or hopeful feeling in our heart, in our gut. And so we still succumb to the frustration presented by the reality of life.
Creating a positive energy flow, as suggested in my recent post, "Changing the Direction of Your Energy Flow - II - Manifesting," is challenging. Definitely possible but challenging, depending on the extent to which you have freed yourself from the control of your ego-mind and reconnected with your heart..
This morning when meditating, I realized that part of the challenge of this suggested form of manifesting is that even this is too specific. It is too easy for the ego-mind to say convincingly that this isn't going to happen, and for the person to be overwhelmed.
An alternative type of manifesting would be about generating a general positive feeling that you will be ok, safe. That it will all work out. That something good will happen, although it may be very different from what you have in mind, and that you will adapt. Somehow, sometime, somewhere. This would require faith, faith in oneself, in your ability to persevere, to free yourself from past ideas and discover new ones, to adapt yourself. And because of this faith you would be able to be present, not think about the future.
The ego-mind will argue against this as well, calling it wishful thinking. But this is neither wishful thinking nor the traditional positive thinking. This is belief in oneself, that one has the ability to adapt and survive on one's own terms.
Ultimately, if you try any form of manifesting of this type (that is, not trying to make something happen), it will require you to have faith in yourself, not just in your talents but in your connection with your true Buddha nature, in your ability to adapt, in your ability to find happiness regardless what life throws your way. If you don't have that faith, then you have to start with that step, which requires beginning to free yourself from the control of your ego-mind and reconnecting with your true self, which is your heart. (See my post, "Freeing Yourself from the Control of Your Ego-mind.") In this case, be prepared that you won't be able to manifest for quite some tome, as freeing yourself, even partially, is challenging.
In the meantime, be present and accept that things are the way they are right now at this moment because it's just the way it is and that it's ok; it will all work itself out. And release all desire that your life be different in any way from the way it is right now at this moment.