Need tips for improvement

Hey guys.. my summoner name is xMado on NA server. I'm a fizz main (second is diana). Recently I went on a losing streak from gold 3 (almost promo for gold 2) all the way down to silver 1. At first I was like 'meh its just a losing streak", however its become way more than that. I'm seriously second guessing my skill and think maybe i belong in silver.. In my games I farm well, know which objectives to go for better than my teammates and 80% of the time at least I win my lane when I play mid. However I am a very aggressive player and I think this is what's doing me in and has caused me to lose so many games. I tunnel vision waaaaaay too much but I CANT STOP. So the question is... What can possibly do to improve my map awareness AND what can I do to stop greed/tunnel vision. Should I start playing support? or a more passive champ? I dont know.. please help!