Monotropic thoughts?

Hi everyone, 
I've struggled for years with constellations of persistent thoughts centred around particular topics. They're often unhealthy - for example when they're focused for weeeks around particular people I really care about who can and will never feel the same way about me. At times these thoughts stop me from focusing on other things that need my attention, because I can't shift my mind from its topic. Is this monotropism? I'm wondering if anyone here has found strategies that have helped with shifting the 'stuckness' of the thoughts? Thanks in advance for any ideas.