Your heart is still beating and there is a lot of life to live. Many people that are middle aged and dating again sometimes lack confidence in their appearance.
You may never truly be over the death of a spouse or the complications of a painful divorce, but you should be at a point where you've grieved enough and you're ready to take life by the horns! If you're not looking for something particularly serious, make sure whoever you are dating knows this.
This should be looked at as a new beginning and maybe you'll feel different if you look different.
That is completely understandable to an extent, but do not feel like who you are right now is not good enough.
Now this does not mean that you cannot reinvent your appearance if thats what you desire.
By all means, change your hairstyle, work on your body at the gym, and buy a new wardrobe if that is truly something that you want to do for yourself.