No way to live your life that mate. I was on the tube last night and wasn't worried at all. Think about it. There's an estimated 5 million journeys done on the tube each day, or nearly 2 billion a year if you prefer. The chances are much less of anything happening there than me being knocked off my bike above ground. Likewise with London Bridge. I make a point of having any business meetings I've got to have in that area. It's perfectly safe, and the vast majority of people are perfectly friendly. You can't let a minuscule minority spoil your life.