I'm very extremist in taharat najasat issues and for me all the things looks najis; even sand on road is also najis. I have bad habits regarding taharat najasat. I mean if I see a kafir person in a restaurant then I do calculations that for sure he have touched the items in kitchen and for sure he have touched my food so food is najis so after eating food thenI will wash all areas and parts of home where I touched while eating and after eating.

Now that you know your problem of being extremist in matters of taharat, you can easily evade it from your mind if you are determined. Many renowned scholars have actually said that consider everything pak (pure) even the water found around the washroom. If shaitan instigates that Allah will be displeased with you and nothing of your worship will be accepted, then say its ok, let it be that way. Go for this notion in everything you see and touch or eat if it be according to the Islamic limits like basically knowing that the food is cooked halal or no najasat (impurity) seen has touched the item you come across. Seeing here is the operative word, and simply not imagining. If you set this rule for yourself, then you are sure to overcome the problem in no time. Remember, it all depends on your will power to change and no one can do that for you except yourself. If you take these first steps, then for sure Allah will take a tenfold for you and reward you for this struggle inshAllah. I pray you and all those facing this problem to show their power against shaitan and win him over, through the power and help of Allah, the All powerful, the All Merciful.