[H] How do I bridge the gap?

Hello everybody, this is my first post here and I have a problem, or more like a confusion as to how I play StarCraft II as opposed to how I view/commentate games I watch. I will explain what I mean as best as I can, but I'll give a little information about myself before as it is my first post and so  you all have an idea as to where I stand on a skill-based standpoint. Long post so if you don't want to read the introduction, skip to the " - - - " lines, that's where my actual problem begins.

I have been playing StarCraft II since the beta. I haven't played in about a year now due to real life issues (cheating girlfriend to be exact). The last time I seriously sat down and tried playing the game was during the first Nvidia Pro/Am Tournament. I main Zerg as I like the instinctual (for the most part) aspects and reactionary playstyle more than Terrans and Protoss' rock-paper-scissors build based style. I practiced hard for two weeks for the tournament, being in Bronze League at the time, I still tested and pushed myself by playing against Diamond players. My brother signed up for the tournament as well, but he got knocked out in the first bracket. I made it to the second round (largely thanks to all the diamonds I had to face in my bracket were default victories because they no-showed), where as my brothers all showed up. I was playing my Zerg where I had my ling/bling/infestor/ultralisk army at max upgrades, including ultra carapace, ling attack speed/move speed, energy for infestors ect., by the 14 minute mark at a max army. I thought it was impressive as the build ran through everybody my level or a little higher, and nobody knew what I was doing because the pros didn't start doing a similar build until about 3-4 months later I think if memory serves. Then I stopped playing before playing any of my round two matches (had to show the new girlfriend at the time she was more important than a game. My bad.) and haven't really played since.

So on to the reason why I write this now that you've gotten an idea kind of where I sit. I currently reside in Silver because Blizzards system doesn't demote me like it should.

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When I play StarCraft II I always get wrecked. I get on, play a couple games, realize how bad I am and get off. I still watch Day[9] every day almost and my brother is always playing so we discuss builds, build options, ect.. during breaks between games. What confuses me, the bridge thing I mentioned in the opening, is that when I play, nothing I do works. I can't explain it really but I basically watch as everything I try gets torn apart. However, when I am shadowing my brother, or obs'ing a game of one of my friends, I'll use my brother for example:

When I watch him play (standing over his shoulder so I see what he sees, and he's almost in Diamond) I can see what he's doing wrong, tell him exactly what he needs to do to fix it to make the game salvageable for a win. I see the army his opponent is making when he scouts and it's like instinctively I'll spew out like, "Get some sentries and immortals to combat his forces." or "get your Colossi up on the ridge right next to you and put your stalkers against the wall so his archon/zealot army can't surround or snipe the Colossi.". Even with my weakest and most uninformed race, Terran, I can see what needs to be done and tell my brother/friends exactly what they need to do to pull out a win, or at least win the engagement. But, when I am in my own games all of that goes out of the window and I'm like "Uh, what the hell do I do?!? Why can't I make what I need to!" and I don't know how to bridge that gap between the two. I don't know if it is just a mechanical or muscle memory issue or what, which is why I am writing this to see if anyone might be able to help me with my problem. I was proud of myself back in the day, being bronze beating diamonds with my build.

Thank you very much in advanced.