How can I stop being such a wimp and stand up for myself more often?

I don't want to be anyone's floor mat. It depends on the situation for me. If something is about to go wrong and I know how to not make go wrong, I speak up about what is going to happen if things aren't approached differently. I work in aviation and I am the answer guy from the factory. It is part of my job to be assertive when I know the results are going to be bad. Sometimes I see my grown children about to do something stupid, the wife gets in one of her moods and I don't like where it is going, I have to make a decision about what I am willing to deal with. I can say my piece or I can remove myself from the equation. Not being assertive is bad for me, and, being too assertive in the wrong situation is bad for me. I would say to try being assertive about things you are confident about and see where it goes.

Learn how to be assertive.

Know what you will and won't accept. And stick to it. Saying no is not the same as being a douchebag

I do same thing. I just keep things bottled up inside me.

You are who you are, you sound submissive

Love yourself more