Mayday = LIFE is in grave or imminent danger. Either it is or isn't and respectfully, any forced landing onto terrain that is 'best choice at the time', the outcome is highly likely to be uncertain, and you are at grave risk of smacking your body into in moving bits at considerable speed. Thinking about it takes mental resources which you need to focus on flying, particularly at low level. Make the call. Cancelling is easy. Getting help is not so.