You've got the answer already. You said, 'I know we are supposed to just live in the moment, be appreciative, get happy, etc.' That's it. It's really that simple. You don't have to send out multiple intentions or find processes to 'let go' you don't have to do anything but "feel good now".

You believe that you will "feel good now" when you have the ring, man etc then you will allow yourself to "feel good now" but what you're doing in this eternal now moment is feeling a cocktail of emotions about not having the man: worry, yearning, insecurity, neediness etc. All those emotions are not a match in vibration to the reality that you want. You'll just keep attracting more scenarios that resemble your vibration of yearning and lack. The Universe can only give you what you're a match to. You're a match to the lack of him so the universe will keep instant manifesting the lack of him for you.

If you were feeling love, appreciation, ecstasy and other 'love' based emotions on a regular basis you would attract all that represents that 'love' back to you. You can only attract into your reality what you're a match to.

If you believe you could use processes to 'let go' and not think about him and yearn for him then you could try them but it doesn't sound to me as if you are at the 'letting go' stage because he is occupying so much of your attention from the 'wanting him but don't have him' vibration so the universe can only bring you the reality of 'wanting him but not having him', because that is a perfect match. It's worth a try though, and I'm sure you will get lots of advice here.

I personally 'let go' of my desires by not allowing any person, event or circumstance distract me from my ultimate goal which is always to feel good now, feel happy now, look for excitement now, feel thankful now, feel appreciation for all the amazingly wonderful things I have in my life now, feel the clearness and the patter sound of the rain lashing against my window now. I'm always turning my attention to all the good things I can see and feel and be excited about now. That works for me. The good stuff just keeps showing up so I know that works :)

know who you are and where you are
going, use the mind to see
deliberative movement,
keeping left and right balanced

Seth talks about this in his book Resonance. He might tell you as one of his students that you are in a phase of the manifestation process, as a conscious co-creator, in which you are making habitual your new regimen, the regimen being your attempts to let go absolutely of your attachments to the other human. As the new desired manifestation takes hold, it dissolves the inertia of the past and creates its own momentum in the physical world.

Another way he describes it is that as you begin a new regimen, or ritual creation of reality, the emotional residue of the past can cloud your perceptions. Your new affirmations of detachment seek to dissolve this residue of desire. In time, your affirmations replace the negative ruminations that bind you to the past. Hope this helps.

your ex as leave you. and you cannot accept it . the simple answer it was is choice. not your choice. what can you do about it nothing. he made the choice to go find someone else now you must do the same. for your ex the page was already turn. it is time for you to turn the page also. If he would have think that you are the person that he want in is life he would still be with you. the fact that he is not tell you something. it is time for you to stop denying the fact and living in the past. know your self and you will know other. if you do not know your self you cannot know other. start to live for your self. put that awareness on you. the ex is gone stop trying to live for him. live for your self. what do you like ? what are you good at? what can you improve for your self? What would you like to experience? Go and do it. on this you have the choice. in this world many time you will not have that choice. They will sell you dream and make you work for it. the big house the big car etc... and all this even if you manage to get it, it will pass away. for the ex it is the same thing you got it now it as went away. and even if the ex came back how long will it last? will the ex make the choice to go again or will you make that choice? know your self and know other.

So what is the method of letting go? or should I saw of living for your self and not being stuck in the past. Is the donkey still running after the carrot? or would the donkey run after the carrot knowing that it will always be out of reach not by is choice?

Right now you live in the past dreaming a future. it would be better for you to live in the moment experiencing wisely the time imparted to you. if I would ask you right now what can you do now and want to do now for your self? do you want to go take a walk? go to the beach? go in the woods? etc...... Can you find it out? or do you wait in the past for a carrot on a stick to move forward?

Control my thoughts and choose not to think about it. Focus on what will make me Happy rather than what to "run" from or what is making me worried.

Focus on what I Have, what I Know, what I Can Do

instead of what I don't have - feeling needy, what I don't know - feeling confusion, and what I can't do - feeling trapped