Thank you for your question. Manifesting dreams and goals have different incubation periods for each individual, based on a variety of conditions. I have found that the biggest hurdle many folks face is surrendering control over to the universe to bring the gifts we desire to us. We fret and stew. We basically focus on the lack of having something instead of allowing opportunities and relationships to evolve naturally. Similar to the saying "A Watched Pot Never Boils " a manifestation seed can't grow optimally when worry, fear, or anxiousness overshadow it.
Also, some people will refuse to "get in the game" by ignoring all the road signs that could have led them to the "pot of gold" they were anticipating.
My advice is to not dwell on whatever it is that you are wanting to happen or changes you desire in your life. State your request and release it to the universal winds to carry it out into the world where it can attract the energies you wish to have return to you. Then, get busy living your life day to day, do whatever you can to find happiness in the moment.
Don't get stuck in "It won't ever happen?" or 'I'm not deserving" types of thoughts. Be willing to accept opportunities from a variety of doors. Since you believe in the "highest good" theory (which I do too)... then make an addendum to your requests by saying something like "I accept this or something better." That allows the universe to shop in the exclusive specialty shops, not limiting it to finding something in the local five-and-dime department store. Of course, I'm simplifying this a bit. Although I don't know why we complicate manifesting the things we love. It doesn't have to be that way at all.
Did I mention that I manifested my DH (dear husband). He appeared three years after I scribbled out the qualifications and characteristics I wanted in a future mate on a rainy afternoon. I then shoved that piece of paper to the back of my dresser drawer and forgot about it. He showed up when I wasn't looking. About six months after I met him I got around to retrieving that piece of paper from underneath my underwear and checked off every item, it was a bit of a surprise to discover he was a perfect match to my list. I was sporting an engagement ring at the time.