What do you mean by the law of attraction? I don't think 'competing' with OW is ever the way to go. However, I think following DB principles is - that means working on detachment, improving yourself (for you) and a possible future partner (or H).
But I think trying to attract him back is probably a time waster, given the probable level of infatuation for OW for now. Best to get out and live your own life for a while - and that has the upside of also being very attractive - but only if you truly do it for you - not to try and win him back. H's with OWs are truly not prizes and your sitch (including OW) probably has to run its natural course.
Take care
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus