OP: When did you pass your test? Have you driven other peoples cars on a long term basis before? The 335i is the first car I have owned too, but I was driving someone else's car for 2 years prior.
I first drove a 335i in Florida and decided I'd like one, that was 3 years ago now and I had barely passed my test back then. It was good fun, but it was 35c outside, the top was down, the roads were empty and each lane out there is the width of the M25. You feel the thrill but there is no danger from traffic. The next year I drove an E550, same kinda thing again, lovely sounding engine and exhaust, sounds great when you floor it. Both powerful cars, but this outside of rush hour and not representative of owning either car on a daily basis.
In December I picked up my 335i, and it was a completely different experience. Roads in the UK are so narrow in comparison and have much more traffic. The surface itself was no where near as grippy due to being much colder and wetter. Also being a manual vs auto the power delivery felt much more involved. Road surfaces are also quite uneven in the UK, you feel the wheels trying to pull the steering in all sorts of directions.
I had a few scares within the first two weeks, you just don't realise how much power this car has. I felt the back end twitch by just going over a white line in the rain whilst accelerating up a slip road. You don't really expect to see a traction control light when accelerating at ~50mph.
I actually ended up leaving mine parked up quite a bit initially and only took it out when the roads were quiet.
Now I am confident driving it but I worry about mundane things. Speedbumps, potholes, parking spaces, not accidentally breaking the speed limit by 20mph when overtaking in a 50. It makes me wonder how people can own a Ferrari in this country.
I wouldn't recommend it as a first car, get a 320d rack up a years NCD and a few thousand miles then trade up. If you want to get an idea of what a 335 will be like make sure its M Sport and still some 19 inch run flats. I'd also recommend becoming friends with a chiropractor