Was in remission and suddenly a nasty flare

I’ve was diagnosed with Ulcerative Colitis in June ,. It eventually settled with Mesalazine and was told in remission. Advised to reduce my medication but another flare up now. Chronic diarrhoea. Steroids now prescribed. Anyone know how long before symptoms ease. I’m due on holiday in 2 weeks. Not feeling I can go at the moment.