As you probably noticed, you will get a lot of opinions on what to do and many of them aren't wrong...but I will tell you how my experience with the game was.
Like you I felt like quitting during the Cleric fight, I had never really played a Souls game before and I just wasn't having fun up to that point; however, it got to be personal with me and I decided that I was going to beat the Cleric no matter what and then put the game away for a while…possibly forever.
When I finally beat the Cleric I had an emotional high that I hadn’t felt in a very long time and I decided to keep playing “for a bit”...I ended up getting the platinum which is not something I typically do.
It’s been said before, but I believe the whole time leading up to the Cleric is an initiation into the game. Once I finished that part I never felt that frustration again for the rest of story, sure I struggled in some areas but I felt that it was just a puzzle that needed to be solved.
That’s basically how I treated every boss fight after the Cleric, I just need to solve the puzzle of each boss. Sometimes being super aggressive and not having to learn the boss worked, sometimes all I needed was a little bit of leveling, sometimes YouTube offered help…but if I was ever really struggling I would always revert back to:
Learn how to dodge/avoid each attack – If you can recognize and react to their moves you can stay alive for a very long time, It makes the bosses feel much less random and overwhelming. It definitely takes some trial and error but not as long as you may think, just experiment with different moves, there’s only so many moves you can do and sometimes staying still is the right one!
Learn when to attack – Now that you can stay alive for a long periods of time and recognize your enemy’s moves, you will begin to notice opportunities for attack. This should come pretty quickly and you will notice that every single boss leaves openings for a safe attack.
I used this approach with quite a few bosses and now feel that I could beat many of them without ever taking a hit…that’s not because I’m “such a good gamer” (I’m not even close), it’s because I broke them down and understand what they are going to do and how to react.
As a side note and generally speaking, staying close and/or being aggressive works well with many of the bosses and will often be a piece in the puzzle.
I know this doesn’t offer specific help for the Cleric, but I found all I really needed was a change in my approach to finally relax and enjoy the game. Hopefully you can enjoy it too!