We should rejoice in our sufferings and tribulations because as we go through them with God we come to rely upon God more and more, we know that through it all God is over all and that He is building into us perseverence, character and hope.
We can understand that God has a plan and a purpose for His people and that everything He does/brings to us has a good purpose even if we don't see it at the time.
Perseverence - We press on because we know God is in control and we can rely on Him even when we think we cannot keep going.
Character - Learning to rely upon God, to allow Him to build our character, to mould us, to teach us, to grow us up in His ways.
Hope - We are not of this world, our hope comes from God above, we look to Him and not worldly things, our hope and knowledge that He has a place prepared for us at the end of time, that His plan is coming to fruition.