We can actually proactively have positive thoughts.

In other words, we  have thoughts that are reasonably valid, that are useful, that cause us to be content and happy and  help us help others: that's called love, kindness, forgiveness, generosity, blah blah blah.

And then  we have low self-esteem and anger and fears and anxiety and jealousy: these ones, you know? But  somehow the unhappy ones seem to come without being invited, don't they? But the other point is,  we can actually actively, proactively have positive thoughts.