It’s a challenge to always be nice and pleasant.
I feel you can say almost anything to a person in a nice way. I try – but it doesn’t always work. So how can one learn?
Emotions get in the way. One first step is getting control of one’s emotions.My rebbi used to say a person’s mind should control their heart not the other way around.
Another is practice talking nicely and weighing one’s words.
Another is learning works of mussar / Jewish ethics – like Duties of the Heart (Chovos ha-Levavos R Bachya ben Joseph ibn Paquda) and Pirkei Avot.
Duties of the Heart – talks about how a Jewish person is to act, feel, think. It is a good start.
In the introduction to the Sefer / Book we read:
Inward service, however, consists of the fulfillment of the Duties of the Heart such as: to acknowledge the Unity of G-d in our hearts, believe in Him and His torah, to undertake His service, that we revere Him and humble ourselves before Him, that we love Him, trust in Him, and give over our lives to Him, that we abstain from what He hates, devote our actions to His Name, that we reflect on the benefits He bestows, and similar things which are performed by the thoughts and sentiments of the heart but do not associate with activity of the visible limbs of the body.
Belief & Trust in G-d is also an important aspect of being pleasant. When a person believes in G-d – knowing that all that comes from Him is for the good – his or her reactions are different than one who lacks trust. A person who trusts Hash-m will understand that all that happens is for the good. Keeping that in mind at all times is a challenge. To do so one can read books like the series “Living Emuna – Living a daily life of Trust in Hashem” By Rabbi David Ashear illuminates practical stories of how simple people who trusted Hash-m were able to overcome many difficulties.
Practice smiling.
Practice connecting.
Become better every day.