Q. If we pray to God to watch over and protect us and if we have guardian angels, then why do bad things happen to us?
A. Prayer is often misunderstood, and is easily a study unto itself. But assuming that one is praying to the one, true God, there are many reason why "bad things" might still occur. Being a true Christian does not instantly make one exempt from hardship. In fact, some Christians find that they go through many more difficulties after they become followers of Jesus.
There are several reasons why we experience problems in this life. Some of the problems and hardships we experience are due to sin in a fallen world. Sin is doing something God says not to or avoiding doing something he commands, and every sin yields a consequence. This may mean anything from feeling convicted to contracting disease. Many people do not understand why a loving God would give harsh consequences to His children, but "the Lord disciplines those he loves," just like an earthly father punishes his own children for misbehaving. (Proverbs 3:12) We never "get away with" sin. Our actions may not always yield immediately apparent consequences, but problems eventually result. If we do not soon come to a point of turning away from our sin and back to God, we should consider whether we truly believe in Him.
Additionally, every time a person sins, people around that person are affected. David's situation in 2 Samuel 11:1-12:19 was an example of this. When David sinned with Bathsheba, he committed adultery, had her husband Uriah murdered and later lost his own son as a result. In addition to the fact that David enabled Bathsheba to sin as well, both their child and Uriah, who were innocent in this circumstance, lost their lives as a result of David's disobedience to God. Remember this the next time you feel the urge to do something that goes against the Word of God. Your choices, even the small ones, do affect others, especially those closest to you.
There are other reasons we experience trials as well. When we speak of "trials," we need to remember that God does not tempt us, as noted in the following verse:
"Let no one say when he is tempted, "I am tempted by God"; for God cannot be tempted by evil, nor does He Himself tempt anyone. But each one is tempted when he is drawn away by his own desires and enticed. Then, when desire has conceived, it gives birth to sin; and sin, when it is full-grown, brings forth death." -James 1:13-15 (NKJV)
So, temptation is not from God, but He does allow trials to happen in our lives so that our faith may be tested and strengthened. The book of Job gives an example of a man who was faithful to God, yet the Lord allowed Satan to take away everything Job had in order that His faith might be tested. Through it all, Job did not deny the Lord.
Trials can also draw us closer to the Lord. These experiences can and should increase our dependence upon Jesus. Many people come to the Lord in prayer only when something is going wrong, and neglect to praise Him when times are good. He may use difficulties to get our attention so that we will come back to Him. Sometimes these circumstances may seem extreme, however the Lord wants us to find our joy in Him, and will use whatever means necessary to draw us back.
After we have gone through difficulties, and sometimes while we are still in them, the Lord can also use us to help others who are going through the same thing. We can be a comfort to others when we can truly sympathize with them. And if we are helping someone through a hardship, this may become an opportunity to share the Gospel and explain how we got through our circumstances by depending on the Lord for strength.
The Lord uses difficult circumstances in our lives for many different reasons. But followers of Jesus can rest assured that He will always do what is best for us, and for His ultimate glory. As we learn to lean on Him through good and bad times, we will be made stronger for it, and perhaps help to strengthen others along the way.
"My brethren, count it all joy when you fall into various trials, knowing that the testing of your faith produces patience. But let patience have its perfect work, that you may be perfect and complete, lacking nothing." -James 1:2-4 (NKJV)
As a side note, it should be made clear that the term "guardian angel" is never used in the Bible, and that term is often misappropriated.