There are three ways you can react when you come across something in your life that indicates that something is happening towards your manifestation i.e. a vibrational match.

1. You can react with positive emotion. Every time you notice something happening and you feel grateful or appreciative that something has happened, you are bringing yourself more and more into alignment with it (assuming you do not think about it in between those things happening). Here, noting down your vibrational matches is accelerating the manifestation into your experience.

2. You can react with no emotion. I have this saying: The neutral point is your friend. What I mean by this is that not having any emotional reaction, positive or negative, about what you want will still enable that thing to manifest for you. This is a huge benefit. It means you never need to think about anything you want again and it will come to you. Notice that you don't have to spend hours daily doing affirmations, visualizations, meditations etc...just let it go and it will come even if you do nothing at all.

3. You can react with negative emotion. This is the problem area. If you think of something and every time you think of it, you feel upset, angry, resentful, annoyed, frustrated (or any similar emotion) that it hasn't come yet, then you are keeping that thing away from you.

This last point is what you seem to be having an issue with, and this usually happens with things that you really want (i.e. things you have a big need for) because otherwise you wouldn't really be that bothered whether it has come yet or not.

The solution to this is to remember that you cannot have your focus in two vibrational places at the same time. That means that if you are feeling grateful or appreciative about something then you cannot also be noticing the absence of it.

Try to do both at once and you'll see that you cannot. You might be able to get your attention to switch between the two quickly but you won't be able to do them simultaneously.

This means that if you are noting down vibrational matches while feeling grateful or appreciative for them, you cannot be in a place of neediness for the thing in that moment.

And if you don't think about the desire again immediately after noting down the vibrational match, you have now left your desire in a better-feeling place than before. Your vibration on any subject always attracts from where you last left it.

Now your feeling about a particular subject could be so strong that you just cannot feel appreciation about it because you only keep noticing it isn't there yet. In that case, noting down your vibrational matches will not serve you.

However, in that case, I would question whether this box experiment approach would be the correct one to use because you may have crossed into desperate need for this thing you want.

You would be better off using a more direct approach of molding your vibration more deliberately. I haven't really gone into detail about how to do this but there are some tips here and Abraham's Ask & It Is Given contains some brilliant systematic methods for this.

In fact, deliberately moving your vibrational setpoint to Appreciation regarding what you want is the fastest way to manifest anything, and is the way I do it with my manifesting spreadsheet. I might try and share my own findings with this more deliberate approach in a future experiment. But I really need people to build up some confidence and experience in manifesting for themselves first and the box experiment is a fairly reliable way to do that if you approach it with the right mindset.

Hope this answers your question a bit.

By the way, just for the sake of having something really trivial to manifest as a kind of demonstration for the box-based approach, I thought I would try manifesting an answer on this website that had more than 10 votes...there's a special badge for that. Last week was very busy and, since it is not something I am at all bothered about, I hadn't got around to writing up the request properly...just noted down a few random thoughts late last week and was going to write it up over the next few days. Well, it manifested exactly while I was writing this answer about not getting too bothered about whether something manifests or not, which I thought was quite amusing. The notification just popped up at the top of my computer screen. The Universe has a great sense of humor if you look for it.