Galatians 6

As the Lord revealed His modern-day Word of Wisdom, he promised -

"...all saints who remember to keep and do these sayings, walking in obedience to the commandments...shall run and not be weary, and shall walk and not faint." (Doctrine and Covenants | Section 89:18 - 20)

At first, one might assume this promise would be a blessing of health, but recalling the words of Isaiah, we read -

"...the LORD, the Creator of the ends of the earth, fainteth not, neither is weary..."(Old Testament | Isaiah 40:28)

And -

"...they that wait upon the LORD shall renew their strength; they shall mount up with wings as eagles; they shall run, and not be weary; and they shall walk, and not faint." (Old Testament | Isaiah 40:31)

I don't think the Lord has a issue of health. I believe when the Lord does not faint or is weary means that we can always depend on Him. I believe that is what is also meant of those that wait upon the Lord. This becomes much clearer with Paul's writing to the Galatians in that -

"...he that soweth to the Spirit shall of the Spirit reap life everlasting.
9 And let us not be weary in well doing: for in due season we shall reap, if we faint not." (New Testament | Galatians 6:8 - 9)

As we have faith in Christ and "wait upon the Lord", we sahll be strengthen. We will not be weary in well doing and will not faint in striving to do so.