Try to get familiar with your natural thought patterns. This is important because awareness has an incredible disarming quality. Next time you sing, the same thoughts might still surface, but the fact that you’re expecting them means that the element of surprise falls away, and so the thought loses power over you.
If you can’t use VHS, it’s likely your DAW has some kind of tape emulation or saturation plugin on hand. If not, FerricTDS is a good free option for PC users, as is Diabolique. Mac and PC users can both check out Klanghelm’s IVGI.