By manifesting frustration, I assume you mean you are manifesting situations in your life that leave you feeling frustrated.

You've hinted that you want to know what it is in your life that you are giving attention to that is causing these frustrating manifestations. Well, there's a fairly simple way of figuring it out.

The key thing to remember is that the Universe manifests according to feeling matches, not subject matches.

What I mean by this is that if, say, your boss is annoying you at work and you feel so constantly frustrated by his/her actions such that you have turned that feeling of frustration into a habitual feeling, you will now start to experience physical manifestations of that feeling.

Perhaps your car won't start (and leaves you feeling frustrated), or perhaps your television stops working (and leaves you feeling frustrated) or perhaps you lose your wallet somewhere (and now you are left feeling frustrated).

Note the common element in those examples...they all left you feeling frustrated...just like your boss does.

In other words, you feeling frustrated about your boss has now manifested other situations (unrelated to your boss) that have left you feeling frustrated.

So, to answer your question about what you are doing that is manifesting frustration, just look at what else in your life causes you to feel frustrated. It should be fairly obvious what the cause is once you've grasped this idea of the universe always matching your feeling rather than the subject of what you are thinking about.

Now following on from what has just been said, consider this...

If the universe always manifests feeling matches, then what would happen if you found something to feel happy about? It doesn't matter what, just anything. And if you can't think of anything, just make up something to feel happy about :)

If you did that to the extent that happiness became a dominant feeling for you, wouldn't the universe have no choice but to start manifesting situations that match happy feelings?

Wouldn't your life then gradually fill up with more and more situations that left you feeling happy (instead of frustrated)?

The answer is yes...that's exactly what would happen.

And what we can deduce from this is that the shortcut to happiness, and happy manifestations, throughout your life is simply to start looking for things to feel happy about.

The feeling must come first, and the manifestations that follow will naturally match the feeling.

Now if you read Muhd's answer understanding that principle, you'll understand why his focusing on love and appreciation is bringing him things he wants i.e. things that match his feeling of love and appreciation.