If you are annoying and aggressive at the start of your career, you will soon gain a reputation for being a right pain in the rear end and work will dry up. You need to be resilient and confident, but also being a nice person will get you further than being nasty.
I can't speak for the modelling industry, but if you want to get into acting, make sure that you have good training as that will begin your journey to making the right contacts. Just emailing agencies for acting will get you nowhere if you don't have the experience. There are thousands of fully trained and experienced actors in the line way ahead of you, so they are more likely to be employed before someone with no training. With modelling, make sure you find a legitimate agency - not one who will take money off you for "training". If you have the right look, you might get an agent. If you don't, you will have to accept that you may be attractive, but not what they are looking for.