Yes we should strive to "be and do our best" in every situation, (translation in God terms: do everything to His glory) but the problem with perfectionism is the inner turmoil that arises with the imperfect. When things aren't "perfect" (which is always), a perfectionist gets all twisted up inside. When my house is in disarray (which is very often with three kids) I can let it affect my mood. Or when my kids disobey a basic tenet of our home for the 5th time before 8 a.m., I get all mangled. Why? Because things should be perfect. (WRONG!)
Things in this life will not be perfect: dings will happen, sickness will come, people will disappoint, spills on just-mopped floors will occur, and money will vanish. But God. His desire for His child is that we rise up inside this rain, amidst the imperfect, and shout "Jesus is Lord!" We cannot do this in our own strength, it's not even possible (especially if you are a perfectionist). But God has given His Spirit to indwell all who name Jesus as their savior. As His child you have the power of God to live victorious in a very imperfect world.
In fact Paul, in 2 Corinthians 12:9-10 explains the victory through the imperfect. "'(God's) grace is sufficient for you, for (His) strength is made perfect in weakness.' Therefore most gladly I will rather boast in my infirmities, that the power of Christ may rest upon me...For when I am weak, then I am strong." Did you get that? When we are faced with the imperfections of this life (sicknesses, reproaches, needs, persecutions, distresses...for Christ's sake), there is strength available from El-Elyon (God Most High) if we seek and trust in Him.
Instead of crying over spilled milk, bless your cat with a drink.