The external world is what it is. The sun rises every morning and sets every night. The season are always the same. Summer is after Spring and before Fall which is followed by winter. There are 24 hours in a day, 7 days a week and 365 days in a year. This has been constant for as far back as humans have existed. Things are what they are and there is nothing you can do to change things or change people.
The only thing we can change is our own perception of how we see things. We can change the meaning we give things. We can change our attitude. We can change how we use our body. We can change what we focus on. Change any of these things and you will get different results out of life. Your outcomes will improve if you improve.
The Serenity Prayer
God, grant me the serenity to accept the things I cannot change,
Courage to change the things I can,
And wisdom to know the difference.Reinhold Niebuhr