sincere sadhana helps in concentration and taper off bad/negative thoughts.I believe, 'fear' or 'lack of confidance' are some of the factors leading to 'negative thoughts'.
Along with 'sadhana' one should be 'true' to him/her self - and should try to keep away from 'anger' / greed / ill thoughts for other.
With all these, the efficiency og mind would be maximum which then offers many alternatives to 'problems'.
jai mata di
Prashant [bhadrakali]