That is kind of an open-ended question and I would say that there is no one answer...
I know what most Baha'is and other religious people would say, that we should be grateful to God for every day, regardless of tests and difficulties, but I do not think that way. That pat answer is much too oversimplified and does not allow for differences in people and their individual circumstances.
I have a problem with forcing a good attitude when I do not have one, it is very dishonest and contrived.
I also have a problem with people who think we should be happy all the time. If they want to be happy, that is their business, but I do not think they should expect everyone else to be happy just because they are. Do they ever even stop to think that other people might have serious problems in their lives, and that everyone cannot deal with them the same way? Apparently not. I consider that very self-centered. Maybe they should stop and think about the effect it might have on other people in a social setting like work where there are many other people around.
I try to have a good attitude but I am not going to pretend I am happy all the time because I cannot be a fake. Someone can now judge me and tell me I am not 'spiritual enough' but only God knows what others endure in life, God and that person and maybe their immediate family.
Moreover, God created a world which is a storehouse of suffering, so something seems amiss when people say that we should be grateful to God for that. In case you never saw the quote:
“O thou seeker of the Kingdom! Thy letter was received. Thou hast written of the severe calamity that hath befallen thee—the death of thy respected husband. That honourable man hath been so subjected to the stress and strain of this world that his greatest wish was for deliverance from it. Such is this mortal abode: a storehouse of afflictions and suffering. It is ignorance that binds man to it, for no comfort can be secured by any soul in this world, from monarch down to the most humble commoner. If once this life should offer a man a sweet cup, a hundred bitter ones will follow; such is the condition of this world. The wise man, therefore, doth not attach himself to this mortal life and doth not depend upon it; at some moments, even, he eagerly wisheth for death that he may thereby be freed from these sorrows and afflictions. Thus it is seen that some, under extreme pressure of anguish, have committed suicide.” Selections From the Writings of ‘Abdu’l-Bahá, p. 200
The question leads the answer. If the alternative is a bad attitude, then of course, good is better. That doesn't necessarily mean you should be happy all the time, even when a tragedy occurs. There are appropriate times to grieve, or to face difficult circumstances. We would not be human if we didn't go through difficult times. Still, happiness is a blessing that we should try to make the most of when we can, and spread that to others.
There is some truth to that but a person can submit to God's Will and not have a good attitude. I think it is dishonest for someone to pretend they have a good attitude when they don't and God will know the difference.
All people cannot be upbeat all the time, but the most important thing is what we do. In the 12 step programs I used to attend they said "feelings just are."
Nothing bothers me more than some people who come around at work with their positive attitude trying to cheer me up when I am struggling just to get through all my problems. I know they do not understand so I have to just grin and bear it. Those people where I work have no conception of how different my life is from theirs. It is not their fault.