These psalms are both reminiscent of other psalms. Ps.70 is taken bodily from Ps. 40. Ps. 71:1-3 is taken from Ps. 31:1-3; and the rest of Ps. 71 is largely made up of fragments also found in other psalms.
What does the Psalmist expert God to be to him, and to do for him, and what will such things make him do? Do you make similar confessions to God when you pray?
Observe the tripe movement in Ps. 71: (a) faith, praying, rise to hope and praise (verses 1-8); (b) faith, under a renewed sense of urgent need, falls back into prayer, and again rises to hope and praise (verse 9-16); (c) faith, for the third driven to prayer, rises quickly to assurance, praise and witness, and there abides (verses 20, 22-24). What does this teach us concerning continuance in prayer?