Are you ever caught between deciding if you should or can?  

"Should I do this?" is another way of saying, "I know it's the right thing to do, but I don't want to put myself on the line. Will you tell me that it's okay? (or not?)" It's the question you ask when you need someone to tell you that you're right - to re-assure you.  

"I can do this." is a statement. It says, "I know I have the ability to do the work."  It's a statement that gives you the authority to choose. Choose what? To act.

Deciding that you can is the lever you need to act.

Choose wisely.