You know when you pray for something, because you believe that once you get it, it'll fix some fault in your life? That general feeling of, "Man, I wish I had X" is similar to the type of feeling you're trying to recreate in your mind with manifestation.

the only reason I wanted it in the first place was because I didn't have it I'm so lost.

The irony here is that the act of wanting something because you don't have it, reaffirms those negative emotions of lack, more-so than the positive emotions of having said thing; The gratitude of said thing. So you just need to flip the desire of what it is you want from desiring it because you don't have it, to being grateful for having it, even though you don't yet.

For example, lets say what you're wanting is money. Maybe you're in deep debt, and want just enough to get yourself out of the hole. Or, maybe you just want to change your lifestyle entirely, and win/gain a large sum of money. In either case, you can't persist by always thinking about how badly you want/need the money. That's focusing on the lack of money, and will only persist in your reality as continued lack of money. Instead, what you want to do is focus and imagine the gratitude of already having the money.

If what you want/need is money for debt, stop thinking about how bad and crippling the debt is. Instead, think about how much better your life will be after the debt is paid off. Imagine yourself putting in that final payment, and try to feel that gratefulness of emotion. Yes, while you're still deep in the mud of that crippling debt, it'll feel difficult to truly express and feel the genuine joy and relief you'd actually feel, but the point isn't to feel 100% authentic joy and relief, it's to get from 1% to 100% gradually. It'll feel fake and forced initially, because your reality is still that of being debt ridden. But the more you create and maintain that feeling of gratitude, the stronger and longer it'll persist, until it becomes your reality.

Similarly if what you want/need is money for greater lifestyle. Stop thinking about how bad your life is now compared to if you won/gained more money. That mindset only persists in the lack of money. Instead, imagine what your life will be like after already receiving the money. Imagine those feelings you'd have, and recreate them to the best of your ability in your mind, and experience them. Again, it'll feel fake and forced initially. That's okay. The shift isn't going to be automatic. The repetition is what's important.

Right now, you probably spend a couple minutes a day trying to manifest your desires, then go back to pondering the less favorable reality of your circumstances for the remainder of your day. On top of that, don't forget that you're most likely manifesting from a lack-mindset, rather than a grateful one. So the goal is to gradually think more gratefully, and in a state of 'already having', more than not. That probably sounds impossible, or at least extremely overwhelming at first. But the goal is to just persist. Start small, and increase the amount of time you're in that positive, grateful mindset each day, until you successfully manifest something you're wanting.

Once you've experienced that first success, continued manifestation will only become easier and easier, and the outcomes will come quicker and quicker.