You're probably thinking, "Tell Me Something I Don't Already Know!" If you grew up swimming as a child, consider yourself one of the lucky ones. Kids who learn how to swim young will always have that innate "feel" for the water. They learned technique at an early age before questions and self-consciousness reared their ugly heads.
Why is swimming so frustrating? Simply put, it's not natural for a human to behave like a fish. We're born to walk, run and breathe on land. Swimming can make us feel uncoordinated, like a literal fish out of water.
Swimming is also one of the most technique driven sports, and it involves a certain "touch" to be both powerful (fast) and graceful (in alignment). That's ultimately what we're seeking in the water, right? Power and speed with a touch of beauty and balance.
If you're not already being coached, seek out a local swim instructor. They will assess your stroke and provide tips and drills to make corrections. Remember you can't change everything overnight, and good coaches will only give you one or two things to think about in each session.