I know what you mean.... but you don't want to learn the lesson by failing. When I was at Uni I was the same as you by the sounds of it... and luckily I came out with a 2:1.

A couple of my friends were I think more intelligent than me, but didn't do enough and got 2:2's - which caused them problems. If the grade isn't too important, then cool. If it is, I reckon the worst thing would be to get a bad mark, and know you could have done more.....

Still, it's all balance... all work & no play and all that....