Easier said than done. Without God's help, such serenity is very very difficult to acquire and keep. If you desire peace in your soul from the Prince of Peace Himself, then you must make supplication.

Be anxious for nothing, but in everything, by prayer and petition, with thanksgiving, present your requests to God. And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus. - Philippians 4:6-7

As a practical measure, I would recommend some moderate fasting and abstinence. Fasting meaning maybe go a day with only water or with a single meal (no need to overstress yourself), and abstinence meaning a decrease in the quality of food for a day (e.g. no meat, no sugar). If you have mastery over your base animal appetites, then mastery over your emotions will become an easier path to follow.

And a lot of liberals I sense are without any peace in their hearts and minds. They are always stressed out and anxious and not resting in God but in material things like drugs, entertainment, sex, and constantly harassed by the demons that oppress them.

Deus Vicit!