You need to build your stamina by exercising and eating right. Do some aerobics and strength training exercises. You could also join a gym for strength training exercises. Weight bearing exercises like climbing stairs and doing some physical work regularly like carrying groceries, lifting objects of weight that is bearable enough to carry helps to strengthen arm muscles. Hope this will help.

Hello
Inner strength and power is not something that you are born with, but it can be developed like any other skill. Your inner strength consists of self discipline, self control, willpower, detachments, persistence, peace of mind, and the ability to concentrate.
It is the ability to overcome temptations, negative habits, laziness, and to carry out actions, even if they are tedious and unpleasant.
Strong Motivation is required to do something. If you have a strong Will power then you can also do things.
Inner Strength Exercised:
Mainly stop comparing yourself with others.
Start Meditation.
Don't read the newspaper for a few days.
Now and then, drink your coffee or tea without sugar.
Climb up the stairs instead of taking the lift.
Park you car a little farther away from you destination, so that you have to walk.
Now and then choose not to watch one of your favorite TV programs.
Read a book that is useful and informative, but which you find boring.
Curb your desire to criticize people.
Delay your desire to retort angrily.
Try to get out of bed quickly on a cold day.

Be Well !!
Regards
Dr. Shilpa Harwani