憂さを晴らす banish depression●dispel one's gloom●dissipate melancholy●drive off [away] one's gloom●get it out of one's system●let [blow, work] off steam●refresh oneself

憂さ晴らしに (in order) to forget it all●as a diversion●for amusement●to distract one from one's grief●to take one's mind off things

憂さ晴らしになる get rid of someone's boredom