The Human Mind craves novelty. It's addictive and it's insatiable. BUT it never leads to mastery.
Focus on a single thing for any substantial amount of time leads to a high level of a mastery and understanding. Spend 1 hour a day doing anything and you will become great at it very quickly. This is the key to greatness.
In EVE that means, you should NOT change ships or fits every day or even every week. You should pick one ship, one fitting, and one tactical plan. THEN you should stay with it, refine it, and develop it to a level of mastery.
Come closer. Listen: I'm going to tell you about a Pirate I met early in my EVE Online Career (I forgot his name unfortunately). When I first met him he killed one of my corp members in a static plex, then when we attempted revenge, he killed more of us. Months later I fit out a ship JUST for fighting him, to exploit his ship and...
He beat me with ease!
This Pirate was unique because he only flew one ship... The Rifter. Over the course of thousands of kills he never once flew any other ships. He was the only "purist" I have ever met in EVE. Needless to say this guy was a bad ass in a Rifter. His focus made him great.
For a more personal example, I can tell you from experience that I see this effect every time I create a new PVP Guide. As part of the creation of the PVP Guide I will fly only one type of ship for weeks or even months. This usually amounts to hundreds of fights and individual experiences.
Usually the first few fights go poorly and I make stupid mistakes, then as time goes on I slowly become very good at flying that ship. I get an instinctual "feel" for the way it accelerates, how fast it kills targets, the tank, when I need to run or turn in, etc. By the time I'm done I can almost fly the ship without thinking, because I have done it so many times.
This effect continues to build over time, the more you train in your ship, the better you will get.
So my advice to everyone new or old is to resist the Shiny New Toy Syndrome and dedicate a few weeks to each ship you fly to give your self a chance to see the effects this focus will have, then should you find a ship you love, consider making that your primary ship. Study it's stats, how it performs against every target you can think of, what the best orbits are for different situations, what damage types to avoid, what implants compliment it the most, which boosters can improve your performance, and on and on.
This focus will lead you to a whole new level of PVP.