"And charity suffereth long, and is kind, and envieth not, and is not puffed up, seeketh not her own, is not easily provoked, thinketh no evil, and rejoiceth not in iniquity but rejoiceth in the truth, beareth all things, believeth all things, hopeth all things, endureth all things." (Moroni 7:45)
"And charity suffereth long" means to me that it never quits. Charity tolerates difficult people and circumstances as best it can without throwing in the towel. How? People with charity know that the other person is not living up to their potential and they just might with a little more patience and encouragement. People with charity endure challenges knowing they have every reason to believe in something better to come. They understand that Christ is "an high priest of good things to come," (Heb. 9:11; see also this video), and they believe in Him and what He has promised them if they have faith in Him.
"And charity suffereth long" doesn't mean that when we have charity we accept the poor choices of others. It means quite the opposite. Because we love that individual we refuse to accept nothing but their best. Elder Dallin H. Oaks said, "those who understand God’s plan for His children know that God’s laws are invariable, which is another great evidence of His love for His children." I recently observed this when a fellow teacher had to impose consequences on a student for not making grades. After reminding the student that he had agreed to such potential consequences and explaining that these would prohibit participation in certain extracurricular activities for a time, this teacher made it overwhelmingly clear that she cared very much for him and his academic performance. He understood and will likely get better grades next term and be allowed to participate once again with his friends.
"And charity suffereth long" really means to me that Christ will never give up on me and those I love. His perfect love tolerates me when I'm difficult because He knows I'm not living up to my potential but that I can with a little patience and encouragement.
Additional note - perhaps one of the most important ways "charity suffereth long" is when we are patient with ourselves and forgive and love ourselves in spite of our mistakes.