Assalamu'alaykum yaa ikhwani fillah,
I'm Indonesian muslimah, a new comer here. I was study Psychology in Indonesian Islamic University. Mmmm....my English isn't very well but I would try to explain my opinion about possitive thinking. Islam has that thing in Akhlaq lesson about husnudzon (ahsanul dzon). An Ulama' from Egypt, Hasan Al Banna (do you know him?), said husnudzon is you should make 1001 reason first before you have bad thinking about yourself or somebody else. The person who has possitive thinking will never said a bad lable to himself (I'm ugly, I'm bad, I'm not cool,etc), or to someone else (she's modest, he's evil, he's rude, etc), or to the unwanted condition (when you get sick, being late, get trouble in work, etc)...The person has high emphatic heart and high tolerance also (salamatush shodr - wide heart). If someone hurt him, he will not reply to hurt. Someone has ever told me, if you hate your teacher - please remember about his kindness to teach you then you get knowledge from him. If you hate a criminal/a bad attitude man/simillar about that, please remember from him you can do da'wah (invite him to the right path of ALLAH). From badness we have a chance to make some or a lot of goodness. So we should becareful to choose a possitive response (thinking, say something, doing anything) between or around bad/negative conditions (taqwa). That's all I know.I know it's hard but it's not impossible. that's why we must have good muslim friend to remind each other (that's why I 'm enjoy this site :-D). Any another good suggestion? Syukran jazilanlakum wa jazaakumullah khoir.
Wassalam