1. Instead of "para que seamos más felices", could we also say "para ser más felices"? - because the subject is the same in the two clauses?
2. With "Ojalá", you point us towards the lesson Using ojalá + the present subjunctive to express hope (El Presente de Subjuntivo) - which illustrates the use of the *present* subjunctive (when expressing a *future* idea). However, perhaps it would be worth emphasising that in this particular writing exercise ("Carmen"), the *imperfect* subjunctive has to be utilised because the speaker is not really referring to the future?
3. You give "al cual que podemos transformar con los pensamientos" as a possible answer, but should the "que" not be removed? - (or if it is permissible, then you should really mention that in the lesson Using preposition a and de + el que, la que, los que, las que = to/of/from/about which/who (relative pronouns) ).
4. (Something very trivial !) > 'Nuestro' has lost its "r" in the Kviziq answer given as "Todos podemos cambiar nuesto modo de pensar".