First of all, not all choline sources are created equal, and they have different mechanisms of action and different processes of metabolism.
So the mood/brain-fog effects of choline really depend on what kind of choline you're taking. If you're taking choline bitartrate/citrate or lecithin then don't worry about it. Those forms must be metabolized first before crossing the blood brain barrier (not actually certain about lecithin, but that's likely the case) which means that your body regulates the amount of acetylcholine increase you'll get in the brain from them.
Alpha-GPC, CDP Choline and DMAE cross the blood brain barrier directly so they require dramatically reduced dosages in comparison. For example you could safely take 6-8grams of lecithin but you'd definitely want to avoid ever taking 6-8 grams of Alpha-GPC. DMAE has a different mechanism of action and there are some great posts by devinthayer on this forum about it (try out that search function).
There are plenty of people taking piracetam without a choline source outside of their normal dietary intake. Personally I found that BBB (blood brain barrier) crossing forms of choline are the number one source for unwanted emotional effects or brain fog. I tried DMAE and it made me dulled out, depressed and spacey.
When I finally run out of choline bitartrate (500g's lasts forever) I'm going to switch to choline citrate, and that's what I'd recommend. Choline is good for a lot of different things in the body. For a lot more info check this link. You can take up to 3.5grams per day safely and side effect free and there isn't much reason to go over that amount.
Since your body regulates it's distribution through metabolism you're unlikely to experience any brain fog or mental-cholinergic side effects. I was taking around 3 grams a day for the first 8 months of the year in three divided doses. Never got any headaches except from nefiracetam but that's a whole-nother thread.