The Amplified Bible puts 1 Thess. 5:18a this way:
Thank [God] in everything [no matter what the circumstances may be, be thankful and give thanks]
Right now, even though our circumstances are much less than perfect, I give thanks to God for you. You have been a light in the darkness over the last few weeks. You have put aside your own important tasks to take over mine, so that I could rest. You have struggled through your own health difficulties, so I could better cope with mine. You have cared for me, the children and the house without complaint. Yes, I am so thankful for you! I can only hope and pray that if the tables were turned I could serve you half as well as you have served me.
I am sorry I was unable to pull out all the stops for you today, but I pray you know that I love you with everything I am. I praise God that I am able to spend my life with you by my side.
Happy Father's Day!
All my love,