How can i do?

What---determiner, pronoun;
What can I do ?
I am sick.

Almost everyone I know was and is still ill to certain degree, mentally and/or physically.  The illness could be as light as having a cold, an allergy, or as heavy as cancer.  Life, just like riding a bike, never proceeds  in a perfect and static way.  You either are a little bit too far to the right or a little too far to the left.  But, you always are able to pull yourself back to the path you want to be on. And until one day, your brakes  are worn or your tires are blown, and then you fall off the bike and complete your experiment on life.

Dude, please do not stop enjoying your life just because you are sick.  Do whatever you can to enjoy the experiment.