Romans 14:13 and 19

Then let us not criticize one another anymore, but rather determine this-not to put an obstacle or stumbling block or a source of temptation in another believer’s way. So then, let us pursue (with enthusiasm) the things which make for peace and the building up of one another (things that lead to spiritual growth).

The best way to stay in peace and love is to stay in the word.  The word will remind us of our own imperfections and keep us humble and less prone to criticize others.  Our hearts flourish when we pursue peace and build up one another and walk in love.  Love is the key to spiritual growth.