We should all try to be sensible about our personal safety (women, as well as men), but having been twice widowed, I am only too aware that there are many instances where it is impossible to be accompanied. I was living alone at the age of 17 up to the age of 27. Widowed at 41 and still working, there were many instances where I had no choice but to cross dark streets or wait on lonely railway platforms by myself (having been to business meetings, for instance). I have gone on holidays alone, even to East Africa one time. It was either go alone, or don't go on holiday at all. Yes, I know there are holidays for singletons - but I was not wanting to meet someone, and these types of holiday are far more expensive than a "standard" holiday. I had friends, but mostly, they were married with children, and not available to travel with me. I have been mugged when walking to work, in the early morning (around 7.30am) when it was light.
We can only try to assess the risks we have to take, and be aware of our surroundings at all times. Take Self Defence classes to give you confidence, and try not to worry too much (being obviously very nervous could make you more vulnerable).