Am i sabotaging any chances i have with love?

i some reason get over guys really fast like liiiiiterally over night one day im stoked on life the next im like ehh im over ittt, also i just always am making up excuses as to why this persons not right for me, i also get tend to think the worst in every situation i KNOW i have let good guys go but i cant figure out if im doing this or are these guys just really not right? can anyone relate?