I don't think life gets harder, I think circumstances change and we adjust to the change. Some people do have issues, but you can't fall....if you're already on the floor.
Only if one chooses to embrace that frame of mind. There is no getting around the fact that life can be very difficult at times. The attitude and perspective you choose to cope with those difficulties is the key to allowing you to handle more than you ever thought you were able to bear.
Depends on the company you keep, your environment and surroundings and ultimately how much knowledge and awareness you have into yourself and what makes you happy or sad.