"Moreover, we have all had human fathers who disciplined us and we respected them for it. How much more should we submit to the Father of spirits and live!" NIV translation
We have all had a parent that guided us in the way that we were to act and, for the most part, earthly fathers are respected. Paul compares these earthly fathers who give us temporary life with our heavenly Father who brings us eternal life. It is only reasonable that the giver of eternal life should be respected and honored even more that one who gives us a temporary physical life.
"They disciplined us for a little while as they thought best; but God disciplines us for our good, in order that we may share in his holiness. No discipline seems pleasant at the time, but painful. Later on, however, it produces a harvest of righteousness and peace for those who have been trained by it." NIV translation
Earthly fathers make mistakes but they usually do the best they can for their children. God does not make mistakes and His motivation is love so we can be sure that whatever we are going through is for our benefit. It may be painful and ugly at the time but, in the end, we will be better off for the working of God in our lives.
"Therefore, strengthen your feeble arms and weak knees. 'Make level paths for your feet,' so that the lame may not be disabled, but rather healed." NIV translation
Paul goes on to exhort us as believers to trust in our heavenly Father. One of the reasons to do so is as an example to others. When bad things happen to Christians, it is an opportunity for us to demonstrate our faith and to explain to others the basis for our faith. In so doing, they will know where to turn when the tough times come to their lives.
The "level paths" refers to the fact that, as Christians, we should be constant in our reliance on God. There are those who cling to Christ during the hard times but, when everything is relatively calm, you cannot even tell that they know the Lord. We are called to praise God at all times and in every situation and that is a true demonstration of faith.