A bridge in a dream usually marks a transition -- the point where you're moving from one state of life into another and need something to carry you across. Crossing it easily can reflect readiness for that change, while a bridge that sways or won't hold your weight often names hesitation about the decision itself.
He that has too great a conceit of himself will be apt to fall into many errors in his judgement; yet on the other side, he that is too diffident, is not fit for this Science. - Cardan Girolamo (1501-1576)