Holding my tongue.

I have a problem. I've been working on this problem for a while, but don't think I've come anywhere close to improving on it. I have a problem holding my tongue. I am sometimes blunt. And sometimes rude. I really do not intend to be rude -- it's not like I plan it or want to hurt someone's feelings. I just say things that I probably shouldn't or should be worded in a more subtle or kinder way.

I've been reading Proverbs every day for the past few months, in hopes of gaining wisdom and restraint. Here's a few verses that I have highlighted, underlined and/or asterisked.

• Proverbs 10:19b: "...he who holds his tongue is wise." 
• Proverbs 17:28: "Even a fool is thought wise if he keeps silent, and discerning if he holds his tongue."

One piece of advice comes from one of the books I'm reading and that is to constantly think of God. If I can keep saying these verses in my head or keep saying to myself "say nothing, keeping your mouth shut", I should do better and sometimes I do. I'm trying to form a new habit and shutting down the old one - it's just taking longer than I hoped. 

That's why I rely on my friends to keep me in check. Call me on me being rude.  Proverbs 19:20: "Listen to advice and accept instruction, and in the end you will be wise." That is what I am counting on. 

Any other ideas on how to change this habit/impulse? I'll take all the advice I can get.