There are multiple reasons not to rejoice in us, but there is EVERY reason to rejoice in the Lord, for He has put away our sins.
In us are groaning and evil, and the consequences thereof. In us, that is our flesh, dwells no good thing. But, in the Lord is FORGIVENESS, mercy, love, and a God that takes the vilest of things and uses it for our good (Ex 34:6-7; Gen 48:16; Ex 6:6). In the Lord is salvation to the uttermost to everyone that believes, and therefore, we rejoice in Him. In the Lord our Savior and not in circumstances is the rejoicing of the elect, for He chose to give us eternal life, in spite of the sins that we commit (Gen 50:20; Rom 9:21).
In the Lord, let us rejoice therefore at all times. Never look upon your circumstances and say, "It is too much. I can't rejoice." Let us never REFUSE our comfort, as the Psalmist did in Ps 77 saying, "This is my infirmity", that he, "refused to be comforted". In Ezra 3:11-13 the people rejoiced and wept because of the temple. Some wept that it was so small, seeing their sins. Others rejoiced that a temple was there at all, rejoicing in deliverance and PRAISING God for what He'd done. Yes, it isn't as great as it could be, but it is BETTER than we deserve and more than we had. It is God's grace in Christ and mercy to sinners. And, rejoicing delivers us from sin. It gives us grace to overcome evil, & it encourages us.
You and I cannot help others in our misery. We must obey the command and rejoice in the Lord - believe the gospel – in spite of our sins. Then, we have something to minister. We have His goodness to sinners, His grace, and we can warn sinners that sin has no joy that lasts, and rejoicing IN the Lord has power to overcome (Rom 6:18).
When you and I first came to Christ, we REJOICED in the Lord and not ourselves. We came with sin, and He put it away. Now, according to Col 2:6-7, we are to walk in Christ as we have received Him, thus rejoicing in Him still. Never let your sin stop you from rejoicing. There is enough in the Lord to conquer circumstances, if we believe. If we refuse our comfort, then it gets worse. But, if we rejoice, then we're delivered, and we learn what we need to learn about sin as we rejoice in Him that conquered it.
In the beginning, He didn't call you to misery but to peace. And, it may have surprised you how joy made you serve. It is the same today (Neh 8:10). The forgiveness, mercy, and joy of the gospel are our strength. Sin is bitter, which is why we rejoice in the Lord who enables us to sin no more.
Never think that salvation can be hindered by you or in any way lessened. It cannot. The same things you and I believe in the good times are the same things that we REJOICE in when times are hard. This turns the bitter into sweet. Thus, rejoice in the Lord, and again, says the Scripture, Rejoice.