Start off with small domestics to get use to waterfed pole method and to build your confidence up. Cleaning high level windows can be tricky if you're unaware of all the potential hazards, i.e. Obstacles to trip over, people nudging behind you as they try to walk past, strong freak gusts of wind, tilt and turn windows not closed properly and many others. Learn to walk before you can run and you'll have no problems working your way up to dizzy heights.