How can i cure my depression ?

so january 2010 was the year i regret.I started smoking bad stuff and sniffing.. you know,in romania opened some illegal substances shops.So i were 17,i enjoyed them like 8month's or so.I quit weed 7months ago and sniffing like 3-4month's ago.I wasn't doing cocaine i was doing some very easy drugs that were legalized by our stupid country romania.Ok after like 3hours passed by the sniff people drooped into depression,and i still feel it like 70% of my time,i regret the first and last lil' drug.How can i deal this depression ?