In general,telling the truth is an important consideration in a relationship because it lay a solid foundation for it.However,nothing is always correct.In my opinion,this issue could only be illustrated on a case by case basis.
Let's take one of my own experience.When I was a junior student,I had a friend whose name is Sam because we both liked to play basketball.On day,he asked me whether he could borrow my basketball which I brought to school,and I agreed with alacrity.When I asked him for my basketball after school,to my surprise,he said some senior students bullied him and took my basketball away.I believed he was telling the truth so I comforted him sympathetically.However,when I went to school on a weekend to take my Math test book,I saw him on the basketball court using my basketball.I raged and shouted to him.Though he explained that he really liked playing basketball but he had no money to buy one for himself,I severed our relationship immediately.In this case,Sam's lie is just a representation of his selfishness,so the lie is absolutely terrible.It would be much better if he had told me the truth,then I would happy to lend my basketball.This example illustrate the importance of telling the truth.
However,as I said in the first paragragh,people do not have to tell the truth all the time.For the final examination last year,we had a mock exam.On the day which we took the mock,one of my classmate got a bad cold and he performed really bad on the mock.After our teacher marked the paper,she didn't told him that he did a bad job,instead she told him that he did quite well and if he could have a good rest before the exam,he could get good grade on it.After listening to the teachers encouragement,he was very confident and had a good rest before the exam.Finally,he really did very well on the final one.In this case,the reason for our teacher to lie is she didn't want to frustrate him before the exam and want him to have a good rest to become healthy again,so I apreciate our teacher's sublime virtue.Of course ,after my classmate know is story,he became a good friend with his teacher.
Concluding from the two examples above,whether we should tell the truth depend on the motive .It is never wrong to lie in order to help a person.