Learn to act on your impulses. The longer you take time to think the more you will be inclined to just sick back and watch. Try to take the initiative in situations such as meeting new people and house maintenance. Be the first the say or do something without thinking about it so much.
It's hard, but there's nothing anyone else can do. You have to make the decision to be active. The only other way is
dualization. This leads to a healthy balance of allowance and rejection or P/J. For INTPs our duals are ESFPs.
Functions are countered in duality as such:
Ti vs Se = Gets your head out of the clouds and down in the real world
Ne vs Fi = You wonder less about objective possibilities and more about what you want.
Si vs Te = You stop living in the past and begin to plan for the future
Fe vs Ni = Your tendency to be indifferent to emotions turns into saying the right word/doing the right thing so you don't hurt feelings.
I can personally attest to the effectiveness if need be.