How can I stop being a pushover?

Take a stand, give insight and opinion, don't sit with a closed mouth and a passive attitude; be more outgoing, personable, social, and in tune with your internal desires; share your internal emotions, strengths, and overall personality in an effort to communicate the best, most admirable side of you; don't settle for other people's judgments, conclusions or assumptions; build yourself up and project your own set of values; take it slow and steady.

I have personally found that willpower is the key to that question. In my opinion, you must learn how to become more cognizant about all the factors in every situation, and push yourself to the maximum. Refuse to be inferior in anything you do from the bottom of your heart, but do not let your ego grow too large in the process. That is my two cents.

Learn to say no. For some reason a lot of us are afraid to tell people no when it comes to things we don't want to do. We need to change that.

yes. One needs to have more confidence and control of your surroundings. Learn to build your self confidence in things you are familiar with.

Start to say no. For little things, very nicely "Oh thank you, that looks delicious, but I'd rather not have another cookie, I'm feeling full." Learn to say no without saying no. Learn to stop saying I'm sorry. Rather than apologizing for being late you could thank people for their patientce. They'll feel better and you won't always hear yourself say sorry. Over time learning to stop saying I'm sorry for mundane things and learning to say no can build a part of your confidence. Your voice, your opinion, you matter!

Start by saying no to the small things. When you find you can say no to a small thing it empowers you. Saying no and standing up for yourself is a skill just like any other. Practice will help you get there.