DD (3yrs) has gone back to sucking her thumb almost constantly, her poor wee thumb is getting calloused and sore from rubbing on her teeth. For a while she had got out of the habit during the day and was just using it to get to sleep at night but we've had a pretty crap time recently which has meant that I've been away a lot (ill family member) and I think this has really unsettled her. Any suggestions for (gently) encouraging her to stop?