I visited two speech therapists about this, but both told me it's not their area of expertise (and subtly hinted that it's not a real problem that needs fixing).
I kept a journal for my _broken_ language habits over about 2 years. I'd then pick one to attack per month. Being conscious about it is hard, but it's doable if you actually make it a goal and track your progress.
Some of the ones I "successfully" killed:
- Stopped using me when my is correct.
- Stopped ending sentences in but (apparently, this is a super specific speech pattern local to my childhood suburb).
- Stopped defaulting to bought and learned to use brought (weirdly, I always knew they were different words when writing, but I would pronounce both as bought).
The one that alludes me:
- Pronouncing 'th' in certain words as 'ef'. Two examples of this are three and north. I've been trying to master this for over a year now (I'm fine with 'three' in most cases, but 'th' at the end of a word still kills me).
Goodluck!