Yeah I've been there. But I don't think you can improve your working memory or your "intelligence" (however you choose to measure it) much beyond your baseline (which could be quite high already, compared to the average). And the only way to stay at your baseline is by having a very relaxed life (good quality sleep, good nutrition and water, exercise etc).
Yearning for a bigger brain only made me feel worse.
Yet, there's this piece inside me that tells me that "the only way out, is through".