Look friends to be more practical and logical I would say by donating blood I am not losing anything but instead adding up new freah blood.
As we all know blood donation is medically suggested every six month. Our body keeps on producing new blood, so whats the harm donating blood and getting fresh in return.

And moreover person like me with all bad habits should be doing quite often.

There is always a personal cause behind every good deeds.
Confused????
Friends that cause can be anything. From greed to personal happiness to satisfaction bla bla bla............

I always say things in this world are relative. It depends on how we take it.

Listen to your heart always.